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ARTIFICIAL  LIGHT 


LIGHT  AND  LIBERTY 


Cbe  Century  JBoofes  of  Xftseful  Science 


Artificial  Light 


ITS  INFLUENCE  UPON  CIVILIZATION 


BY 


M.  LUCKIESH 


DIRECTOR  OF  APPLIED  SCIENCE.  NELA  RESEARCH  LABORATORY, 
NATIONAL  LAMP  WORKS  OF  GENERAL  ELECTRIC  COMPANY 

Author  of  “Color  and  Its  Applications,”  “Light  and  Shade 
and  Their  Applications,”  “The  Lighting  Art,” 

“The  Language  of  Color,”  etc. 


ILLUSTRATED  WITH 
PHOTOGRAPHS 


NEW  YORK 
THE  CENTURY  CO. 
1920 


Copyright,  1 920,  by 
The  Century  Co. 


THE  GET?/  CEiViL, 
LIBRARY 


DEDICATED 

TO  THOSE  WHO  HAVE  ENCOURAGED 
ORGANIZED  SCIENTIFIC  RESEARCH  FOR 
THE  ADVANCEMENT  OF  CIVILIZATION 


PREFACE 


In  the  following  pages  I  have  endeavored  to  discuss 
artificial  light  for  the  general  reader,  in  a  manner  as 
devoid  as  possible  of  intricate  details.  The  early 
chapters  deal  particularly  with  primitive  artificial  light 
and  their  contents  are  generally  historical.  The 
science  of  light-production  may  be  considered  to  have 
been  born  in  the  latter  part  of  the  eighteenth  century 
and  beginning  with  that  period  a  few  chapters  treat  of 
the  development  of  artificial  light  up  to  the  present 
time.  Until  the  middle  of  the  nineteenth  century  mere 
light  was  available,  but  as  the  century  progressed,  the 
light-sources  through  the  application  of  science  be¬ 
came  more  powerful  and  efficient.  Gradually  mere 
light  grew  to  more  light  and  in  the  dawn  of  the  twen¬ 
tieth  century  adequate  light  became  available.  In  a 
single  century,  after  the  development  of  artificial  light 
began  in  earnest,  the  efficiency  of  light-production  in¬ 
creased  fifty-fold  and  the  cost  diminished  correspond¬ 
ingly.  The  next  group  of  chapters  deals  with  various 
economic  influences  of  artificial  light  and  with  some  of 
the  byways  in  which  artificial  light  is  serving  man¬ 
kind.  On  passing  through  the  spectacular  aspects  of 
lighting  we  finally  emerge  into  the  esthetics  of  light 
and  lighting. 

The  aim  has  been  to  show  that  artificial  light  has  be¬ 
come  intricately  interwoven  with  human  activities  and 


IX 


X 


PREFACE 


that  it  has  been  a  powerful  influence  upon  the  progress 
of  civilization.  The  subject  is  too  extensive  to  be 
treated  in  detail  in  a  single  volume,  but  an  effort  has 
been  made  to  present  a  discussion  fairly  complete  in 
scope.  It  is  hoped  that  the  reader  will  gain  a  greater 
appreciation  of  artificial  light  as  an  economic  factor, 
as  an  artistic  medium,  and  as  a  mighty  influence  upon 
the  safety,  efficiency,  health,  happiness,  and  general 
progress  of  mankind. 


M.  Luckiesh. 


ACKNOWLEDGMENTS 


It  is  a  pleasant  duty  to  acknowledge  the  cooperation 
of  various  companies  in  obtaining  the  photographs 
which  illustrate  this  book.  With  the  exception  of 
Plates  2  and  7,  which  are  reproduced  from  the  excellent 
works  of  Benesch  and  Allegemane  respectively,  the 
illustrations  of  early  lighting  devices  are  taken  from 
an  historical  collection  in  the  possession  of  the  National 
Lamp  Works  of  the  General  Electric  Co.  To  this 
company  the  author  is  indebted  for  Plates  1,  3,  4,  5,  6, 
9,  11,  15,  18b,  20,  21,  29;  to  Dr.  McFarlan  Moore  for 
Plate  10;  to  Macbeth  Evans  Glass  Co.  for  Plate  12;  to 
the  Corps  of  Engineers,  U.  S.  Army,  for  Plate  13;  to 
Lynn  Works  of  G.  E.  Co.  for  Plates  14,  16;  to  Edison 
Lamp  Works  of  G.  E.  Co.  for  Plates  17,  24;  to  Cooper 
Hewitt  Co.  for  Plate  18a;  to  R.  U.  V.  Co.  for  Plate  19; 
to  New  York  Edison  Co.  for  Plates  22,  26,  30;  to  W. 
D’A.  Ryan  and  the  Schenectady  Works  of  G.  E.  Co.  for 
Plates  23,  25,  31 ;  to  National  X-Ray  Reflector  Co.  for 
Plate  28.  Besides  the  companies  and  the  individuals 
particularly  involved  in  the  foregoing,  the  author  is 
glad  to  acknowledge  his  appreciation  of  the  assistance 
of  others  during  the  preparation  of  this  volume. 


CONTENTS 


CHAPTER  PAGE 

I  Light  and  Progress . 3 

II  The  Art  of  Making  Fire . 15 

III  Primitive  Light-Sources . 24 

IV  The  Ceremonial  Use  of  Light . 38 

V  Oil-Lamps  of  the  Nineteenth  Century  .  .  51 

VI  Early  Gas-Lighting . 63 

VII  The  Science  of  Light-Production  ....  80 

VIII  Modern  Gas-Lighting . 97 

IX  The  Electric  Arcs . Ill 

X  The  Electric  Incandescent  Filament  Lamps  127 

XI  The  Light  of  the  Future . 143 

XII  Lighting  the  Streets . 152 

XIII  Lighthouses . 163 

XIV  Artificial  Light  in  Warfare . 178 

XV  Signaling . 194 

XVI  The  Cost  of  Light . 208 

XVII  Light  and  Safety . 225 

XVIII  The  Cost  of  Living . 238 

XIX  Artificial  Light  and  Chemistry  ....  256 

XX  Light  and  Health . 269 

XXI  Modifying  Artificial  Light . 284 

XXII  Spectacular  Lighting . 298 

XXIII  The  Expressiveness  of  Light . 310 

XXIV  Lighting  the  Home . 325 

XXV  Lighting — A  Fine  Art? . 341 

Reading  References . 357 

Index  . 359 


LIST  OF  ILLUSTRATIONS 

Light  and  Liberty . Frontispiece 

FACING 

PAGE 

Primitive  fire-baskets . 16 

Crude  splinter-holders . 16 

Early  open-flame  oil  and  grease  lamps . 17 

A  typical  metal  multiple-wick  open-flame  oil-lamp  .  .  32 

A  group  of  oil-lamps  of  two  centuries  ago . 33 

Lamps  of  a  century  or  two  ago . 56 

Elaborate  fixtures  of  the  age  of  candles . 57 

Flame  arc . 128 

Direct  current  arc . 128 

On  the  testing-racks  of  the  manufacturer  of  incandescent 

filament  lamps . 129 

Carbon-dioxide  tube  for  accurate  color-matching  .  .  .  160 

The  Moore  nitrogen  tube . 160 

Modern  street  lighting . 161 

A  completed  lighthouse  lens . 176 

Torro  Point  Lighthouse,  Panama  Canal . 176 

American  search-light  position  on  Western  Front  in  1919  177 
American  standard  field  search-light  and  power  unit  .  .  177 

Signal-light  for  airplane . 232 

Trench  light-signaling  outfit . 232 

Aviation  field  light-signal  projector . 232 

Signal  search-light  for  airplane . 232 

Unsafe,  unproductive  lighting  worthy  of  the  dark  ages  .  233 

The  same  factory  made  safe,  cheerful,  and  more  produc¬ 
tive  by  modern  lighting . 233 

Locomotive  electric  headlight . 240 

Search-light  on  a  fire-boat . 240 


XIV 


ILLUSTRATIONS 


FACING 

PAGE 

Building  ships  under  artificial  light  at  Hog  Island  Ship¬ 
yard  . 241 

Artificial  light  in  photography . 256 

Sterilizing  water  with  radiant  energy  from  quartz  mer¬ 
cury-arcs  . 257 

Judging  color  under  artificial  daylight . 272 

Artificial  daylight . 273 

Fireworks  and  illuminated  battle-fleet  at  Hudson-Fulton 

Celebration . 288 

Fireworks  exhibition  on  May  Day  at  Panama-Pacific  Ex¬ 
position  . 289 

The  new  flood  lighting  contrasted  with  the  old  outline 

lighting . 304 

Niagara  Falls  flooded  with  light . 305 

Artificial  light  honoring  those  who  fell  and  those  who 
returned . 320 

The  expressiveness  of  light  in  churches . 321 

Obtaining  two  different  moods  in  a  room  by  a  portable 
lamp  which  supplies  direct  and  indirect  components 
of  light  .  336 

The  lights  of  New  York  City . 337 

Artificial  light  in  community  affairs . 352 

Panama-Pacific  Exposition . 353 


ARTIFICIAL  LIGHT 


ARTIFICIAL  LIGHT 


i 

LIGHT  AND  PROGRESS 

The  human  race  was  born  in  slavery,  totally  sub¬ 
servient  to  nature.  The  earliest  primitive  beings 
feasted  or  starved  according  to  nature’s  bounty  and 
sweltered  or  shivered  according  to  the  weather.  When 
night  fell  they  sought  shelter  with  animal  instinct,  for 
not  only  were  activities  almost  completely  curtailed  by 
darkness  but  beyond  its  screen  lurked  many  dangers. 
It  is  interesting  to  philosophize  upon  a  distinction  be¬ 
tween  a  human  being  and  the  animal  just  below  him  in 
the  scale,  but  it  may  serve  the  present  purpose  to  dis¬ 
tinguish  the  human  being  as  that  animal  in  whom  there 
is  an  unquenchable  and  insatiable  desire  for  independ¬ 
ence.  The  effort  to  escape  from  the  bondage  of  nature 
is  not  solely  a  human  instinct ;  animals  burrow  or  build 
retreats  through  the  instinct  of  self-preservation.  But 
this  instinct  in  animals  is  soon  satisfied,  whereas  in 
human  beings  it  has  been  leading  ever  onward  toward 
complete  emancipation. 

The  progress  of  civilization  is  a  long  chain  of  count¬ 
less  achievements  each  one  of  which  has  increased 
man’s  independence.  Early  man  perhaps  did  not  con¬ 
ceive  the  idea  of  fire  and  then  set  out  to  produce  it. 

3 


4 


ARTIFICIAL  LIGHT 


His  infant  mind  did  not  operate  in  this  manner.  But 
when  he  accidentally  struck  a  spark,  produced  fire  by 
friction,  or  discovered  it  in  some  other  manner,  he  saw 
its  possibility.  It  is  thrilling  to  picture  primitive  man 
at  his  first  bonfire,  enjoying  the  warmth,  or  at  least 
interested  in  it.  But  how  wonderful  it  must  have  be¬ 
come  as  twilight’s  curtain  was  drawn  across  the  heav¬ 
ens  !  This  controllable  fire  emitted  light.  It  is  easy 
to  imagine  primitive  man  pondering  over  this  phenome¬ 
non  with  his  sluggish  mind.  Doubtless  he  cautiously 
picked  up  a  flaming  stick  and  timidly  explored  the 
crowding  darkness.  Perhaps  he  carried  it  into  his  cave 
and  behold!  night  had  retreated  from  his  abode!  No 
longer  was  it  necessary  for  him  to  retire  to  his  bed  of 
leaves  when  daylight  failed.  The  fire  not  only  banished 
the  chill  of  night  but  was  a  power  over  darkness. 
Viewed  from  the  standpoint  of  civilization,  its  discovery 
was  one  of  the  greatest  strides  along  the  highway  of 
human  progress.  The  activities  of  man  were  no  longer 
bounded  by  sunrise  and  sunset.  The  march  of  civil¬ 
ization  had  begun. 

In  the  present  age  of  abundant  artificial  light,  with 
its  manifold  light-sources  and  accessories  which  have 
made  possible  countless  applications  of  light,  mankind 
does  not  realize  the  importance  of  this  comfort.  Its 
wonderful  convenience  and  omnipresence  have  resulted 
in  indifference  toward  it  by  mankind  in  general,  not¬ 
withstanding  the  fact  that  it  is  essential  to  man’s 
most  important  and  educative  sense.  By  extinguishing 
the  light  and  pondering  upon  his  helplessness  in  the 
resulting  darkness,  man  may  gain  an  idea  of  its  over¬ 
whelming  importance.  Those  unfortunate  persons  who 


LIGHT  AND  PROGRESS 


suffer  the  terrible  calamity  of  blindness  after  years  of 
dependence  upon  sight  will  testify  in  heartrending 
terms  to  the  importance  of  light.  Milton,  whose  eye¬ 
sight  had  failed,  laments, 

0  first  created  beam  and  thou  great  Word 

“Let  there  be  light,”  and  light  was  over  all, 

Why  am  I  thus  bereaved  thy  prime  decree? 

Perhaps  only  through  a  similar  loss  would  one  fully 
appreciate  the  tremendous  importance  of  light  to  him, 
but  imagination  should  be  capable  of  convincing  him 
that  it  is  one  of  the  most  essential  and  pleasure-giving 
phenomena  known  to  mankind. 

A  retrospective  view  down  the  vista  of  centuries  re¬ 
veals  by  contrast  the  complexity  with  which  artificial 
light  is  woven  into  human  activities  of  the  present  time. 
Written  history  fails  long  before  the  primitive  races 
are  reached,  but  it  is  safe  to  trust  the  imagination  to 
penetrate  the  fog  of  unwritten  history  and  find  early 
man  huddled  in  his  cave  as  daylight  wanes.  Impelled 
by  the  restless  spirit  of  progress,  this  primitive  being 
grasped  the  opportunity  which  fire  afforded  to  extend 
his  activities  beyond  the  boundaries  of  daylight.  The 
crude  art  upon  the  walls  of  his  cave  was  executed  by 
the  flame  of  a  smoking  fagot.  The  fire  on  the  ledge  at 
the  entrance  to  his  abode  became  .a  symbol  of  home,  as 
the  fire  on  the  hearth  lias  symbolized  home  and  hospi¬ 
tality  throughout  succeeding  ages.  The  accompanying 
light  and  the  protection  from  cold  combined  to  establish 
the  home  circle.  The  ties  of  mated  animals  expanded 
through  these  influences  to  the  bonds  of  family.  Thus 
light  was  woven  early  into  family  life  and  has  been 


6 


ARTIFICIAL  LIGHT 


throughout  the  ages  a  moralizing  and  civilizing  influ¬ 
ence.  To-day  the  residence  functions  as  a  home  mainly 
under  artificial  light,  for  owing  to  the  conditions  of 
living  and  working,  the  family  group  gathers  chiefly 
after  daylight  has  failed. 

From  the  pine  knot  of  primitive  man  to  the  wonder¬ 
fully  convenient  light-sources  of  to-day  there  is  a  great 
interval,  consisting,  as  appears  retrospectively,  of 
small  and  simple  steps  long  periods  apart.  Measured 
by  present  standards  and  achievements,  development 
was  slow  at  first  and  modern  man  may  be  inclined  to 
impatience  as  he  views  the  history  of  light  and  human 
progress.  But  the  achievements  of  early  centuries, 
which  appear  so  simple  at  the  present  time,  were  really 
great  accomplishments  when  considered  in  the  light  of 
the  knowledge  of  those  remote  periods.  Science  as  it 
exists  to-day  is  founded  upon  proved  facts.  The  sci¬ 
entist,  equipped  with  a  knowledge  of  physical  and 
chemical  laws,  is  led  by  his  imagination  into  the  dark¬ 
ness  of  the  unexplored  unknown.  This  knowledge 
illuminates  the  pathway  so  that  hypotheses  are  intelli¬ 
gently  formed.  These  evolve  into  theories  which  are 
gradually  altered  to  fit  the  accumulating  facts,  for  along 
the  battle  area  of  progress  there  are  innumerable  scout  - 
ing-parties  gaining  secrets  from  nature.  These  are 
supported  by  individuals  and  by  groups,  who  verify, 
amplify,  and  organize  the  facts,  and  they  in  turn  are 
followed  by  inventors  who  apply  them.  Liaison  is 
maintained  at  all  points,  but  the  attack  varies  from 
time  to  time.  It  may  be  intense  at  certain  places  and 
other  sectors  may  be  quiet  for  a  time.  There  are  occa¬ 
sional  reverses,  but  the  whole  line  in  general  pro- 


LIGHT  AND  PROGRESS 


7 


gresses.  Each  year  witnesses  the  acquirement  of  new 
territory.  It  is  seen  that  through  the  centuries  there 
is  an  ever-growing  momentum  as  knowledge,  efficiency, 
and  organization  increase  the  strength  of  this  invading 
army  of  scientists  and  inventors. 

The  burning  fagot  rescued  mankind  from  the  shackles 
of  darkness,  and  the  grease-lamp  and  tallow-candle 
have  done  their  part.  Progress  was  slow  in  those  early 
centuries  because  the  great  minds  of  those  ages  philoso¬ 
phized  without  a  basis  of  established  facts:  scientific 
progress  resulted  more  from  an  accumulation  of  acci¬ 
dental  discoveries  than  by  a  directed  attack  of  philoso¬ 
phy  supported  by  the  facts  established  by  experiment. 
It  was  not  until  comparatively  recent  times,  at  most 
three  centuries  ago,  that  the  great  intellects  turned  to 
systematically  organized  scientific  research.  Such  men 
as  Newton  laid  the  foundation  for  the  tremendous 
strides  of  to-day.  The  store  of  facts  increased  and  as 
the  attitude  changed  from  philosophizing  to  investigat¬ 
ing,  the  organized  knowledge  grew  apace.  All  of  this 
paved  the  way  for  the  momentous  successes  of  the  pres¬ 
ent  time. 

The  end  is  not  in  sight  and  perhaps  never  will  be. 
The  unexplored  region  extends  to  infinity  and,  judged 
by  the  past,  the  momentum  of  discovery  will  continue 
to  increase  for  ages  to  come,  unless  the  human  race 
decays  through  the  comfort  and  ease  gained  from 
utilizing  the  magic  secrets  which  are  constantly  being 
wrested  from  nature.  Among  the  achievements  of 
science  and  invention,  the  production  and  application 
of  artificial  light  ranks  high.  As  an  influence  upon 
civilization,  no  single  achievement  surpasses  it. 


8 


ARTIFICIAL  LIGHT 


Without  artificial  light,  mankind  would  be  compara¬ 
tively  inactive  about  one  half  its  lifetime.  To-day  it 
has  been  fairly  well  established  that  the  human  organ¬ 
ism  can  flourish  on  eight  hours’  sleep  in  a  period  of 
twenty-four  hours.  Another  eight  hours  spent  in  work 
should  settle  man’s  obligation  to  the  world.  The  re¬ 
maining  hours  should  be  his  own.  Artificial  light  has 
made  such  a  distribution  of  time  possible.  The  work¬ 
ing-periods  in  many  cases  may  be  arranged  in  the  in¬ 
terests  of  economy,  which  often  means  continuous 
operations.  The  sun  need  not  be  considered  when  these 
operations  are  confined  to  interiors  or  localized  out¬ 
doors. 

Thus,  artificial  light  has  been  an  important  factor 
in  the  great  industrial  development  of  the  present  time. 
Man  now  burrows  into  the  earth,  navigates  under 
water,  travels  upon  the  surface  of  land  and  sea,  and 
soars  among  the  clouds  piloted  by  light  of  his  own  mak¬ 
ing.  Progress  does  not  halt  at  sunset  but  continues 
twenty-four  hours  each  day.  Building,  printing,  manu¬ 
facturing,  commerce,  and  other  activities  are  prose¬ 
cuted  continuously,  the  working-shifts  changing  at  cer¬ 
tain  periods  regardless  of  the  rising  or  setting  sun. 
Adequate  artificial  lighting  decreases  spoilage,  in¬ 
creases  production,  and  is  a  powerful  factor  in  the  pre¬ 
vention  of  industrial  accidents. 

It  has  ever  been  true  since  the  advent  of  artificial 
light  that  the  intellect  has  been  largely  nourished  after 
the  completion  of  the  day’s  work.  The  highly  de¬ 
veloped  artificial  lighting  of  the  present  time  may  ac¬ 
count  for  much  of  the  vast  industry  of  publication. 
Books,  magazines,  and  newspapers  owe  much  to  con- 


LIGHT  AND  PROGRESS 


9 


venient  and  inexpensive  artificial  light,  for  without  it 
fewer  hours  would  be  available  for  recreation  and  ad¬ 
vancement  through  reading.  Schools,  libraries,  and 
art  museums  may  be  attended  at  night  for  the  better¬ 
ment  of  the  human  race.  The  immortal  Lincoln,  it  is 
said,  gained  his  early  education  largely  by  the  light  of 
the  fireplace.  But  all  were  not  endowed  with  the  per¬ 
sistence  of  Lincoln,  so  that  illiteracy  was  more  common 
in  his  day  than  in  the  present  age  of  adequate  illumina¬ 
tion. 

The  theatrical  stage  not  only  depends  for  its  effect¬ 
iveness  upon  artificial  light  but  owes  its  existence  and 
development  largely  to  this  agency.  In  the  moving- 
picture  theater,  pictures  are  projected  upon  the  screen 
by  means  of  it  and  even  the  production  of  the  pictures 
is  independent  of  daylight.  These  and  a  vast  number 
of  recreational  activities  owe  much,  and  in  some  cases 
their  existence,  to  artificial  light. 

Not  many  centuries  ago  the  streets  at  night  were 
overrun  by  thieves  and  to  venture  outdoors  after  dark 
was  to  court  robbery  and  even  bodily  harm.  In  these 
days  of  comparative  safety  it  is  difficult  to  realize  the 
influence  that  abundant  illumination  has  had  in  increas¬ 
ing  the  safety  of  life  and  property.  Maeterlinck  in  his 
poetical  drama,  “The  Bluebird/’  appropriately  has 
made  Light  the  faithful  companion  of  mankind.  The 
Palace  of  Night,  into  which  Light  is  not  permitted  to 
enter,  is  the  abode  of  many  evils.  Thus  the  poet  has 
played  upon  the  primitive  instincts  of  the  impressive¬ 
ness  of  light  and  darkness. 

By  combining  the  symbolism  of  light,  color,  and 
darkness  with  the  instincts  which  have  been  inherited 


10 


ARTIFICIAL  LIGHT 


by  mankind  from  its  superstitious  ancestry  of  the  age 
of  mythology,  another  field  of  application  of  artificial 
light  is  opened.  Light  has  gradually  assumed  such 
attributes  as  truth,  knowledge,  progress,  enlightenment. 
Throughout  the  early  ages  light  was  more  or  less  wor¬ 
shiped  and  thus  artificial  lights  became  woven  in  many 
religious  ceremonies.  Some  of  these  have  persisted  to 
the  present  time.  The  great  pageants  of  peace  cele¬ 
brations  and  world’s  expositions  appropriately  feature 
artificial  light.  In  drawing  upon  the  potentiality  of  the 
expressiveness  and  impressiveness  of  light  and  color, 
artificial  light  is  playing  a  major  part.  Doubtless  the 
future  generations  will  be  entertained  by  gorgeous 
symphonies  of  light.  Experiments  are  performed  in 
this  direction  now  and  then,  and  it  is  reasonable  to 
expect  that  after  many  centuries  of  cultivation  of  the 
appreciation  of  light-symphonies,  these  will  take  a  place 
among  the  arts.  The  elaborate  and  complicated  music 
of  the  present  time  is  appreciated  by  civilized  nations 
only  after  many  centuries  of  slow  cultivation  of  taste 
and  understanding. 

Light-therapy  is  to-day  a  distinct  science  and  art. 
The  germicidal  action  of  light-rays  and  of  some  of  the 
invisible  rays  which  ordinarily  accompany  the  luminous 
rays  is  well  proved.  Wounds  are  treated  effectively 
and  water  is  sterilized  by  the  ultraviolet  radiant  energy 
in  modern  artificial  illuminants. 

Thousands  of  lighthouses,  light-ships,  and  light- 
buoys  are  scattered  along  sea-coasts,  rivers,  and  chan¬ 
nels.  They  guide  the  wheelman  and  warn  the  lookout 
of  shoals  and  reefs.  Some  of  these  send  forth  flashes 
of  light  whose  intensities  are  measured  in  millions  of 


LIGHT  AND  PROGRESS 


11 


candle-power.  Many  are  unattended  for  days  and  even 
months.  These  powerful  lights  dominated  by  auto¬ 
matic  mechanisms  have  replaced  the  wood-hres  which 
were  maintained  a  few  centuries  ago  upon  certain 
prominent  points. 

Signal-lights  now  guide  the  railroad  train  through 
the  night.  A  burning  flare  dropped  from  the  rear  of  a 
train  keeps  the  following  train  at  a  safe  distance. 
Huge  search-lights  penetrate  the  night  air  for  many 
miles.  When  these  are  equipped  with  shutters,  a  code 
may  be  flashed  from  one  ship  to  another  or  between  the 
vessel  and  land.  A  code  from  a  powerful  search-light 
has  been  read  a  hundred  miles  away  because  the  flashes 
were  projected  upon  a  layer  of  high  clouds  and  were 
thus  visible  far  beyond  the  horizon. 

Artificial  light  played  its  part  in  the  recent  war. 
Huge  search-light  equipments  were  devised  for  porta¬ 
bility.  This  mobile  apparatus  was  utilized  against 
enemy  aircraft  and  in  various  other  ways.  Small 
hand-lamps  are  used  to  send  out  a  pencil  of  light  as 
directed  by  a  pair  of  sights  and  the  code  is  flashed  by 
means  of  a  trigger.  Raiding-parties  are  no  longer  con¬ 
cealed  by  the  curtain  of  darkness,  for  rockets  and  star- 
shells  are  used  to  illuminate  large  areas.  Flares  sent 
upward  to  drift  slowly  downward  supported  by  para¬ 
chutes  saved  and  cost  many  lives  during  the  recent 
war.  Rockets  are  used  by  ships  in  distress  and  also 
by  beleaguered  troops. 

Experiments  are  being  prosecuted  to  ascertain  the 
possibilities  of  artificial  light  in  the  forcing  of  plant- 
growth,  and  even  chickens  are  made  to  work  longer 
hours  by  its  use. 


12 


ARTIFICIAL  LIGHT 


Artificial  light  is  now  modified  in  color  or  spectral 
character  to  meet  many  requirements.  Daylight  has 
been  reproduced  in  spectral  quality  so  that  certain 
processes  requiring  accurate  discrimination  of  color  are 
now  prosecuted  twenty-four  hours  a  day  under  artificial 
daylight.  Colored  light  is  made  of  the  correct  quality 
which  does  not  affect  photographic  plates  of  various 
sensibilities.  Monochromatic  light  is  utilized  in  photo¬ 
micrography  for  the  best  rendition  of  detail.  Light¬ 
waves  have  been  utilized  as  standards  of  length  be¬ 
cause  they  are  invariable  and  fundamental.  Numerous 
other  interesting  adaptations  of  artificial  light  are  in 
daily  use. 

This  is  in  reality  the  age  of  artificial  light,  for  man¬ 
kind  has  not  only  become  independent  of  daylight  in 
certain  respects,  but  has  improved  upon  natural  light. 
The  controllability  of  artificial  light  makes  it  superior 
to  natural  light  in  many  ways.  In  fact,  uses  have  been 
made  of  artificial  light  which  are  impossible  with  nat¬ 
ural  light.  Light-sources  may  be  made  of  a  vast  vari¬ 
ety  of  shapes,  and  these  may  be  transported  wherever 
desired.  They  may  be  equipped  with  reflectors  and 
other  optical  devices  to  direct  or  to  diffuse  the  light  as 
required. 

Thus,  artificial  light  to-day  has  numerous  advantages 
over  light  which  has  been  furnished  by  the  Creator. 
It  is  sometimes  stated  that  it  can  never  compete  with 
daylight  in  cheapness,  inasmuch  as  the  latter  costs 
nothing.  But  this  is  not  true.  Even  in  the  residence, 
daylight  costs  something,  because  windows  are  more 
expensive  than  plain  walls.  The  expense  of  washing 
windows  is  an  appreciable  percentage  of  the  cost  of 


LIGHT  AND  PROGRESS  13 

gas  or  electricity.  And  there  is  window-breakage  to  be 
considered. 

In  the  more  elaborate  buildings  of  the  congested  por¬ 
tions  of  cities,  daylight  is  satisfactory  a  lesser  number 
of  hours  than  in  the  outlying  districts.  In  some  stores, 
offices,  and  factories  artificial  light  is  used  throughout 
the  day.  Still,  the  daylighting-equipment  is  installed 
and  maintained.  Furthermore,  when  it  is  considered 
that  much  expensive  area  is  given  to  light-courts  and 
much  valuable  wall  space  to  windows,  it  is  seen  that  the 
cost  of  daylight  in  congested  cities  is  in  reality  con¬ 
siderable.  Of  course,  the  daylighting-equipment  has 
value  in  ventilating,  but  ventilation  may  be  taken  care 
of  in  a  very  satisfactory  manner  as  a  separate  problem. 

The  cost  of  skylights  in  museums  and  other  large 
buildings  is  far  greater  than  that  of  ordinary  ceilings 
and  walls,  and  the  extra  allowance  for  heating  is  ap¬ 
preciable.  The  expense  of  maintenance  of  some  sky¬ 
lights  is  considerable.  Thus  it  is  seen  that  the  cost 
and  maintenance  of  daylighting-equipment,  the  loss  of 
valuable  rental  space  and  of  wall  area,  and  the  in¬ 
creased  expense  of  heating  are  factors  which  challenge 
the  statement  that  daylight  costs  nothing.  In  fact,  it  is 
not  surprising  to  find  that  occasionally  the  elimination 
of  daylighting — the  reliance  upon  artificial  light  alone 
— has  been  seriously  contemplated.  When  the  possi¬ 
bilities  of  the  latter  are  considered,  it  is  reasonable  to 
expect  that  it  will  make  greater  and  greater  inroads 
and  that  many  buildings  of  the  future  will  be  equipped 
solely  with  artificial-lighting  systems. 

Naturally,  with  the  tremendous  development  of  arti¬ 
ficial  light  during  the  present  age,  a  new  profession  has 


14 


ARTIFICIAL  LIGHT 


arisen.  The  lighting  expert  is  evolving  to  till  the  needs. 
He  is  studying  the  problems  of  producing  and  utilizing 
artificial  illumination.  He  deals  with  the  physics  of 
light-production.  His  studies  of  utilization  carry  him 
into  the  vast  fields  of  physiology  and  psychology.  His 
is  a  profession  which  eventually  will  lead  into  numer¬ 
ous  highways  and  byways  of  enterprise,  because  the 
possibilities  of  lighting  extend  into  all  those  activities 
which  make  their  appeal  to  consciousness  through  the 
doorway  of  vision.  These  possibilities  are  limited  only 

bv  the  boundaries  of  human  endeavor  and  in  the  broad- 
«/ 

est  sense  extend  even  beyond  them,  for  light  is  one  of 
the  most  prominent  agencies  in  the  scheme  of  creation. 
It  contributes  largely  to  the  safety,  the  efficiency,  and 
the  happiness  of  civilized  beings  and  beyond  all  it  is  a 
powerful  civilizing  agency. 


II 


THE  ART  OF  MAKING  FIRE 

Scattered  over  the  earth  at  the  present  time  various 
stages  of  civilization  are  to  be  found,  from  the  primi¬ 
tive  savages  to  the  most  highly  cultivated  peoples.  Al¬ 
though  it  is  possible  that  there  are  tribes  of  lowly  be¬ 
ings  on  earth  to-day  unfamiliar  with  fire  or  ignorant 
of  its  uses,  savages  are  generally  able  to  make  fire. 
Thus  the  use  of  fire  may  serve  the  purpose  of  distin¬ 
guishing  human  beings  from  the  lower  animals. 
Surely  the  savage  of  to-day  who  is  unable  to  kindle  fire 
or  who  possesses  a  mind  as  yet  insufficiently  developed 
to  realize  its  possibilities,  is  quite  at  the  mercy  of 
nature’s  whims.  He  lives  merely  by  animal  prowess 
and  differs  little  in  deeds  and  needs  from  the  beasts  of 
the  jungle.  In  this  imaginary  journey  to  the  remote 
regions  beyond  the  outskirts  of  civilization  it  soon  be¬ 
comes  evident  that  the  development  of  artificial  light 
may  be  a  fair  measure  of  civilization. 

In  viewing  the  development  of  artificial  light  it  is 
seen  that  preceding  the  modern  electrical  age,  man  de¬ 
pended  universally  upon  burning  material.  Obviously, 
the  course  of  civilization  has  been  highly  complex  and 
cannot  be  symbolized  adequately  by  the  branching 
tree.  From  its  obscure  beginning  far  in  the  impene¬ 
trable  fog  of  prehistoric  times,  it  has  branched  here 
and  there.  These  various  branches  have  been  sub¬ 
jected  to  many  different  influences,  with  the  result  that 

15 


16 


ARTIFICIAL  LIGHT 


some  flourished  and  endured,  some  retrogressed,  some 
died,  some  went  to  seed  and  fell  to  take  root  and  to  be¬ 
gin  again  the  upward  climb.  The  ultimate  result  is 
the  varied  civilization  of  the  present  time,  a  study  of 
which  aids  in  penetrating  the  veil  that  obscures  the 
ages  of  unrecorded  writing.  Likewise,  material  relics 
of  bygone  ages  supply  some  threads  of  the  story  of 
human  progress  and  mythology  aids  in  spanning  the 
misty  gap  between  the  earliest  ages  of  man  and  the 
period  when  historic  writings  were  begun.  Through¬ 
out  these  various  stages  it  becomes  manifest  that  the 
development  of  artificial  light  is  associated  with  the 
progress  of  mankind. 

According  to  a  certain  myth,  Prometheus  stole  fire 
from  heaven  and  brought  this  blessing  to  earth. 
Throughout  the  mythologies  of  various  races,  fire  and, 
as  a  consequence,  light  have  been  associated  with  divin¬ 
ity.  They  have  been  subjects  of  worship  perhaps  more 
generally  than  anything  else,  and  these  early  impres¬ 
sions  have  survived  in  the  ceremonial  uses  of  light  and 
fire  even  to  the  present  time.  The  origin  of  fire  as 
represented  in  any  of  the  myths  of  the  superstitious 
beings  of  early  ages  is  as  suitable  as  any  other,  inas¬ 
much  as  definite  knowledge  is  unavailable.  Active 
volcanoes,  spontaneous  combustion,  friction,  acciden¬ 
tal  focusing  of  the  sun’s  image,  and  other  means  may 
have  introduced  primitive  beings  to  fire.  A  study  of 
savage  tribes  of  the  present  age  combined  with  a  sur¬ 
vey  of  past  history  of  mythology,  of  material  relics, 
and  of  the  absence  of  lamps  or  other  lighting  utensils 
leads  to  the  conclusion  that  the  earliest  source  of  light 
was  the  wood  fire. 


PRIMITIVE  FIRE-BASKETS 


CRUDE  SPLINTER-HOLDERS 


EARLY  OPEN-FLAME  OIL  AND  GREASE  LAMPS 


THE  AET  OF  MAKING  FIRE 


17 


Even  to-day  the  savages  of  remote  lands  have  not 
advanced  further  than  the  wood-fire  stage,  and  they 
may  be  found  kneeling  upon  the  ground  energetically 
but  skilfully  rubbing  sticks  together  until  the  friction 
kindles  a  fire.  In  using  these  fire-sticks  they  convert 
mechanical  energy  into  heat  energy.  This  is  a  funda¬ 
mental  principle  of  physics,  employed  by  them  as  neces¬ 
sity  demands,  but  they  are  totally  ignorant  of  it  as  a 
scientific  law.  The  things  which  these  savages  learn 
are  the  result  of  accidental  discovery.  Until  man  pon¬ 
dered  over  such  simple  facts  and  coordinated  them  so 
that  he  could  extend  his  knowledge  by  general  reason¬ 
ing,  his  progress  could  not  be  rapid.  But  the  sluggish 
mind  of  primitive  man  is  capable  of  devising  improve¬ 
ments,  however  slowly,  and  the  art  of  making  fire  by 
means  of  rubbing  fire- sticks  gradually  became  more  re¬ 
fined.  Mechanical  improvements  resulted  from  expe¬ 
rience,  with  the  consequence  that  finally  one  stick  was 
rubbed  to  and  fro  in  a  groove,  or  was  rapidly  twirled 
between  the  palms  of  the  hands  while  one  end  was 
pressed  firmly  into  a  hole  in  a  piece  of  wood.  In  the 
course  of  a  few  seconds  or  a  minute,  depending  upon 
skill  and  other  conditions,  a  fire  was  obtained.  It  is 
interesting  to  note  how  civilized  man  is  often  compelled 
by  necessity  to  adopt  the  methods  of  primitive  beings. 
The  rubbing  of  sticks  is  an  emergency  measure  of  the 
master  of  woodcraft  at  the  present  time,  and  the  pro¬ 
duction  of  fire  in  this  manner  is  the  proud  accomplish¬ 
ment  or  ambition  of  every  Boy  Scout. 

Where  only  such  crude  means  of  kindling  fire  were 
available  it  became  the  custom  in  some  cases  to  main¬ 
tain  a  fire  burning  continuously  in  a  public  place. 


18 


AKTIFICIAL  LIGHT 


Around  this  pyrtaneum  the  various  civil,  political,  and 
religious  affairs  were  carried  on  by  the  light  and 
warjnth  of  the  public  fire.  Many  quaint  customs 
evolved,  apparently,  from  this  ancient  procedure. 

The  tinder-box  of  modern  centuries  doubtless  orig¬ 
inated  in  very  early  times,  for  it  is  inconceivable  that 
the  earliest  beings  did  not  become  aware  of  the  pro¬ 
duction  of  sparks  when  certain  stones  were  struck  to¬ 
gether.  In  the  stone  age,  when  human  beings  spent 
much  of  their  time  chiseling  implements  and  utensils 
from  stone  by  means  of  tools  of  the  same  substance, 
it  appears  certain  that  this  means  of  producing  fire 
was  ever  apparent.  Many  of  their  sharp  implements, 
such  as  knives  and  arrow-heads,  were  made  of  quartz 
and  similiar  material  and  it  is  likely  that  the  use  of  two 
pieces  of  quartz  for  producing  a  spark  originated  in 
those  remote  periods.  Alaskan  and  Aleutian  tribes 
are  known  to  have  employed  two  pieces  of  quartz  cov¬ 
ered  with  native  sulphur.  When  these  were  struck  to¬ 
gether  with  skill,  excellent  sparks  were  obtained. 

Later,  when  iron  and  steel  became  available,  the  more 
modern  tinder-box  was  developed.  An  early  applica¬ 
tion  of  the  flint-and-steel  principle  was  made  by  certain 
Esquimo  tribes  who  obtained  fire  by  striking  a  piece 
of  quartz  against  a  piece  of  iron  pyrites.  The  latter 
is  a  yellow  sulphide  of  iron,  of  crystalline  form,  best 
known  as  “fool’s  gold.”  Doubtless,  the  more  primi¬ 
tive  beings  used  dried  grass,  leaves,  and  moss  as  in¬ 
flammable  material  upon  which  the  sparks  were  show¬ 
ered.  In  later  centuries  the  tinder-box  was  filled 
with  charred  grass,  linen,  and  paper.  There  was  a 
long  interval  between  the  development  of  fire-sticks 


THE  ART  OF  MAKING  FIRE 


19 


and  that  of  the  tinder-box  as  measured  by  the  progress 
of  civilization.  During  recent  centuries  ordinary 
brown  paper  soaked  in  saltpeter  and  dried  was  util¬ 
ized  satisfactorily  as  an  inflammable  material.  Such 
devices  have  been  employed  in  past  ages  in  widely 
separated  regions  of  the  earth.  Elaborate  specimens 
of  tinder-boxes  from  Jamaica,  Japan,  China,  Europe, 
and  various  other  countries  are  now  reposing  in  the 
collections  in  the  possession  of  museums  and  of  indi¬ 
viduals. 

If  the  radiant  energy  from  the  sun  is  sufficiently 
concentrated  upon  inflammable  material,  the  latter  will 
ignite.  Such  concentration  may  be  achieved  by  means 
of  a  convex  lens  or  a  concave  mirror.  This  method  of 
producing  fire  does  not  antedate  the  more  primitive 
methods  such  as  striking  quartz  or  rubbing  wooden 
sticks,  because  the  materials  required  are  not  readily 
found  or  prepared,  but  it  is  of  very  remote  origin. 
Aristophanes  in  his  comedy  “The  Clouds,”  which  is 
a  satire  aimed  at  the  science  and  philosophy  of  his 
period  (488-385  b.c.),  mentions  the  “burning  lens.” 
Nearly  every  one  is  familiar  with  an  achievement  at¬ 
tributed  to  Archimedes  in  which  he  destroyed  the  ships 
at  Syracuse  by  focusing  the  image  of  the  sun  upon 
them  by  means  of  a  concave  mirror.  The  ancient 
Egyptians  were  proficient  in  the  art  of  glass-making, 
so  it  is  likely  that  the  “burning-glass”  was  employed 
by  them.  Even  a  crude  lens  of  glass  will  focus  an 
image  of  the  sun  sufficiently  well  to  cause  inflammable 
material  to  ignite. 

The  energy  in  sunlight  varies  enormously,  even  on 
clear  days,  because  the  water-vapor  in  the  atmosphere 


20 


ARTIFICIAL  LIGHT 


absorbs  some  of  the  radiant  energy  emitted  by  the  sun. 
This  absorbed  radiation  is  chiefly  known  as  infra-red 
energy,  which  does  not  arouse  the  sensation  of  light. 
When  the  water-vapor  content  of  the  atmosphere  is 
high,  the  sun,  though  it  may  appear  as  bright  to  the 
eye,  in  reality  is  not  as  hot  as  it  would  be  if  the  water- 
vapor  were  not  present.  However,  a  fire  may  be  kin¬ 
dled  by  concentrating  only  the  visible  rays  in  sunlight 
because  of  the  enormous  intensity  of  sunlight.  A  con¬ 
vex  lens  fashioned  from  ice  by  means  of  a  sharp-edged 
stone  and  finally  shaped  by  melting  the  surfaces  as 
they  are  rubbed  in  the  palms  of  the  hands,  will  kindle 
a  fire  in  highly  inflammable  material  if  the  sun  is  high 
and  the  atmosphere  is  fairly  clear.  Burning-glasses 
are  used  to  a  considerable  extent  at  the  present  time 
in  certain  countries  and  it  is  reported  that  British  sol¬ 
diers  were  supplied  with  them  during  the  Boer  War. 
Indicative  of  the  predominant  use  to  which  the  glass 
lens  was  applied  in  the  past  is  the  employment  of  the 
term  “burning-glass”  instead  of  lens  in  the  scientific 
writings  as  late  as  a  century  or  two  ago. 

As  civilization  advanced,  leading  intellects  began  to 
inquire  into  the  mysteries  of  nature  and  the  periods  of 
pure  philosophy  gave  way  to  an  era  of  methodical  re¬ 
search.  Alchemy  and  superstition  began  to  retire  be¬ 
fore  the  attacks  of  those  pioneers  who  had  the  temerity 
to  believe  that  the  scheme  of  creation  involved  a  vast 
network  of  invariable  laws.  In  this  manner  the  pow¬ 
erful  sciences  of  physics  and  chemistry  were  born  a 
few  centuries  ago.  Among  other  things  the  produc¬ 
tion  of  fire  and  light  received  attention  and  the  “dark 
ages”  were  doomed  to  end.  The  crude,  uncertain,  and 


THE  ART  OF  MAKING  FIRE  21 

inconvenient  methods  of  making  fire  were  replaced  by 
steadily  improving  scientific  devices. 

Matches  were  at  first  cumbersome,  dangerous,  and 
expensive,  but  these  gradually  evolved  into  the  safety 
matches  of  the  present  time.  Although  they  were  pri¬ 
marily  intended  for  lighting  fires  and  various  kinds 
of  lamps,  billions  of  them  are  now  used  yearly  as  con¬ 
venient  light-sources.  Smoldering  hemp  or  other  ma¬ 
terial  treated  with  niter  and  other  substances  was  an 
early  form  of  match  used  especially  for  discharging 
firearms.  The  modern  wax-taper  is  an  evolutionary 
form  of  this  type  of  light- source. 

Phosphorus  has  long  played  a  dominant  role  in  the 
preparation  of  matches.  The  first  attempt  at  making 
them  in  their  modern  form  appears  to  have  occurred 
about  1680.  Small  pieces  of  phosphorus  were  used  in 
connection  with  small  splints  of  wood  dipped  in  sul¬ 
phur.  This  type  of  match  did  not  come  into  general 
use  until  after  the  beginning  of  the  nineteenth  cen¬ 
tury,  owing  to  its  danger  and  expense.  White  or  yel¬ 
low  phosphorus  is  a  deadly  poison ;  therefore  the  prog¬ 
ress  of  the  phosphorus  match  was  inhibited  until  the 
discovery  of  the  relatively  harmless  form  known  as  red 
phosphorus.  The  first  commercial  application  of  this 
form  was  made  in  about  1850. 

An  early  ingenious  device  consisted  of  a  piece  of 
phosphorus  contained  in  a  tube.  A  piston  fitted 
snugly  into  the  tube,  by  means  of  which  the  air  could 
be  compressed  and  the  phosphorus  ignited.  Sulphur 
matches  were  ignited  from  the  burning  tinder,  the  lat¬ 
ter  being  fired  by  flint  and  steel.  In  1828  another  form 
of  match  consisted  of  a  glass  tube  containing  sulphuric 


22 


ARTIFICIAL  LIGHT 


acid  and  surrounded  by  a  mixture  of  chlorate  of  potash 
and  sugar.  A  pair  of  nippers  was  supplied  with  each 
box  of  these  “matches,”  by  means  of  which  the  tip  of 
the  glass  tube  could  be  broken  off.  This  liberated  the 
acid,  which  upon  mixing  with  the  other  ingredients  set 
tire  to  them.  To  this  contrivance  a  roll  of  paper  was 
attached  which  was  ignited  by  the  burning  chemicals. 

The  lucifer  or  friction  matches  appeared  in  about 
1827,  but  successful  phosphorus  matches  were  first 
made  in  about  1833.  The  so-called  safety  match  of 
the  present  time  was  invented  in  the  year  1855.  To¬ 
day  the  total  daily  output  of  matches  reaches  millions 
and  perhaps  billions.  Automatic  machinery  is  em¬ 
ployed  in  preparing  the  splints  of  wood  and  in  dipping 
them  into  molten  paraffin  wax  and  finally  into  the  ig¬ 
niting  composition. 

During  recent  years  the  principle  of  the  tinder-box 
has  been  revived  in  a  device  in  which  sparks  are  pro¬ 
duced  by  rubbing  the  mineral  cerite  (a  hydrous  silicate 
of  cerium  and  allied  metals)  against  steel.  These 
sparks  ignite  a  gas-jet  or  a  wick  soaked  in  a  highly  in¬ 
flammable  liquid  such  as  gasolene  or  alcohol.  This 
device  is  a  tinder-box  of  the  modern  scientific  age. 

Naturally  with  the  advent  of  electricity,  electrical 
sparks  came  into  use  for  lighting  gas-jets  and  mantles 
and  in  isolated  instances  they  have  served  as  light- 
sources.  Doubtless,  every  one  is  familiar  with  the 
parlor  stunt  of  igniting  a  gas-jet  from  the  discharge 
from  the  finger-tips  of  static  electricity  accumulated 
by  shuffling  the  feet  across  the  floor- rug. 

Although  many  of  these  methods  and  devices  have 


THE  ART  OF  MAKING  FIRE 


23 


been  used  primarily  for  making  fire,  they  have  served 
as  emergency  or  momentary  light-sources.  In  the  out¬ 
skirts  of  civilization  some  of  them  are  employed  at 
the  present  time  and  various  modern  light-sources  re¬ 
quire  a  method  of  ignition. 


Ill 


PRIMITIVE  LIGHT-SOURCES 

Many  are  familiar  with  the  light  of  the  firefly  or  of 
its  larvae,  the  glow-worm,  but  few  persons  realize  that 
a  vast  number  of  insects  and  lower  organisms  are  en¬ 
dowed  with  the  superhuman  ability  of  producing  light 
by  physiological  processes.  Apparently  the  chief  func¬ 
tion  of  these  lighting-plants  within  the  living  bodies  is 
not  to  provide  light  in  the  sense  that  the  human  being 
uses  it  predominantly.  That  is,  these  wonderful  light- 
sources  seem  to  be  utilized  more  for  signaling,  for  lur¬ 
ing  prey,  and  for  protection  than  for  strictly  illuminat¬ 
ing-purposes.  Much  study  has  been  given  to  the  pro¬ 
duction  of  light  by  animals,  because  the  secrets  will 
be  extremely  valuable  to  mankind.  As  one  floats  over 
tide-water  on  a  balmy  evening  after  dark  and  watches 
the  pulsating  spots  of  phosphorescent  light  emitted  by 
the  lowly  jellyfishes,  his  imaginative  mood  formulates 
the  question,  “Why  are  these  lowly  organisms  en¬ 
dowed  with  such  a  wonderful  ability!” 

Despite  his  highly  developed  mind  and  body  and  his 
boasted  superiority,  man  must  go  forth  and  learn  the 
secrets  of  light-production  before  he  may  emancipate 
himself  from  darkness.  If  man  could  emit  light  in  rel¬ 
ative  proportion  to  his  size  as  compared  with  the  fire¬ 
fly,  he  would  need  no  other  torch  in  the  coal-mine. 
How  independent  he  would  be  in  extreme  darkness 

24 


PRIMITIVE  LIGHT-SOURCES 


25 


where  his  adapted  eyes  need  only  a  feeble  light-source ! 
Primitive  man,  desiring  a  light-source  and  having  no 
means  of  making  fire,  imprisoned  the  glowing  insects 
in  a  perforated  gourd  or  receptacle  of  clay,  and  thus 
invented  the  first  lantern  perhaps  before  he  knew  how 
to  make  fire.  The  fireflies  of  the  West  Indies  emit  a 
continuous  glow  of  considerable  luminous  intensity 
and  the  natives  have  used  these  imprisoned  insects  as 
light-sources.  Thus  mankind  has  exhibited  his  su¬ 
periority  by  adapting  the  facilities  at  hand  to  the 
growing  requirements  which  his  independent  nature 
continuously  nourished.  His  insistent  demand  for  in¬ 
dependence  in  turn  has  nourished  his  desire  to  learn 
nature’s  secrets  and  this  desire  has  increased  in  in¬ 
tensity  throughout  the  ages. 

The  act  of  imprisoning  a  glowing  insect  was  in  it¬ 
self  no  greater  stride  along  the  highway  of  progress 
than  the  act  of  picking  a  tasty  fruit  from  its  tree. 
However,  the  crude  lantern  perhaps  directed  his  primi¬ 
tive  mind  to  the  possibilities  of  artificial  light.  The 
flaming  fagot  from  the  fire  was  the  ancestor  of  the  oil- 
lamp,  the  candle,  the  lantern,  and  the  electric  flash¬ 
light.  It  is  a  matter  of  conjecture  how  much  time 
elapsed  before  his  feeble  intellect  became  aware  that 
resinous  wood  afforded  a  better  light-source  than  woods 
which  were  less  inflammable.  Nevertheless,  pine  knots 
and  similar  resinous  pieces  of  wood  eventually  were 
favored  as  torches  and  their  use  has  persisted  until 
the  present  time.  In  some  instances  in  ancient  times 
resin  was  extracted  from  wood  and  burned  in  vessels. 
This  was  the  forerunner  of  the  grease-  and  the  oil- 
lamp.  In  the  woods  to-day  the  craftsman  of  the  wilds 


26 


ARTIFICIAL  LIGHT 


keeps  on  the  lookout  for  live  trees  saturated  with 
highly  inflammable  ingredients. 

Viewed  from  the  present  age,  these  smoking,  flicker¬ 
ing  light-sources  appear  very  crude;  nevertheless  they 
represent  a  wide  gulf  between  their  users  and  those 
primitive  beings  who  were  unacquainted  with  the  art 
of  making  fire.  Although  the  wood  fire  prevailed  as  a 
light-source  throughout  uncounted  centuries,  it  was 
subjected  to  more  or  less  improvement  as  civilization 
advanced.  When  the  wood  fire  was  brought  indoors 
the  day  wTas  extended  and  early  man  began  to  develop 
his  crude  arts.  He  thought  and  planned  in  the  com¬ 
fort  and  security  of  his  cave  or  hut.  By  the  firelight 
he  devised  implements  and  even  decorated  his  stone 
surroundings  with  pictures  which  to-day  reveal  some¬ 
thing  of  the  thoughts  and  activities  of  mankind  during 
a  civilization  which  existed  many  thousand  years  ago. 

When  it  was  too  warm  to  have  a  roaring  fire  upon 
the  hearth,  man  devised  other  means  for  obtaining  light 
without  undue  warmth.  He  placed  glowing  embers 
upon  ledges  in  the  walls,  upon  stone  slabs,  or  even  upon 
suspended  devices  of  non-inflammable  material.  Later 
he  split  long  splinters  of  wood  from  pieces  selected 
for  their  straightness  of  grain.  These  burning  splin¬ 
ters  emitting  a  smoking,  feeble  light  were  crude  but 
they  were  refinements  of  considerable  merit.  A  testi¬ 
monial  of  their  satisfactoriness  is  their  use  throughout 
many  centuries.  Until  very  recent  times  the  burning 
splinter  has  been  in  use  in  Scotland  and  in  other  coun¬ 
tries,  and  it  is  probable  that  at  present  in  remote  dis¬ 
tricts  of  highly  civilized  countries  this  crude  device 
serves  the  meager  needs  of  those  whose  requirements 


PRIMITIVE  LIGHT-SOURCES 


27 


have  been  undisturbed  by  the  progress  of  civilization. 
Scott,  in  “The  Legend  of  Montrose/’  describes  a  table 
scene  during  a  feast.  Behind  each  seat  a  giant  High¬ 
lander  stood,  holding  a  blazing  torch  of  bog-pine.  This 
was  also  the  method  of  lighting  in  the  Homeric  age. 

Crude  clay  relics  representing  a  human  head,  from 
the  mouth  of  which  the  wood-splinters  projected,  ap¬ 
pear  to  corroborate  the  report  that  the  flaming  splinter 
was  sometimes  held  in  the  mouth  in  order  that  both 
hands  of  a  workman  would  be  free.  Splinter-holders 
of  many  types  have  survived,  but  most  of  them  are  of 
the  form  of  a  crude  pedestal  with  a  notch  or  spring 
clip  at  its  upper  end.  The  splinter  was  held  in  this 
clip  and  burned  for  a  time  depending  upon  its  length 
and  the  character  of  the  wood.  It  was  the  business  of 
certain  individuals  to  prepare  bundles  of  splinters, 
which  in  the  later  stages  of  civilization  were  sold  at 
the  market-place  or  from  house  to  house.  Those  who 
have  observed  the  frontiersman  even  among  civilized 
races  will  be  quite  certain  that  the  wood  for  splinters 
was  selected  and  split  with  skill,  and  that  the  splinters 
were  burned  under  conditions  which  would  yield  the 
most  satisfactory  light.  It  is  a  characteristic  of  those 
who  live  close  to  nature,  and  are  thus  limited  in  facili¬ 
ties,  to  acquire  a  surprising  efficiency  in  their  primitive 
activities. 

An  obvious  step  in  the  use  of  burning  wood  as  a 
light-source  was  to  place  such  a  fire  on  a  shelf  or  in  a 
cavity  in  the  wall.  Later  when  metal  was  available, 
gratings  or  baskets  were  suspended  from  the  ceiling 
or  from  brackets  and  glowing  embers  or  flaming  chips 
were  placed  upon  them.  Some  of  these  were  equipped 


28 


ARTIFICIAL  LIGHT 


with  crude  chimneys  to  carry  away  the  smoke,  and  per¬ 
haps  to  increase  the  draft.  In  more  recent  centuries 
the  first  attempt  at  lighting  outdoor  public  places  was 
by  means  of  metal  baskets  in  which  flaming  wood 
emitted  light.  It  was  the  duty  of  the  watchman  to 
keep  these  baskets  supplied  with  pine  knots.  In  early 
centuries  street-lighting  was  not  attempted,  and  no 
serious  efforts  worthy  of  consideration  as  adequate 
lighting  were  made  earlier  than  about  a  century  ago. 
As  a  consequence  the  “  link-boy  ”  came  into  existence. 
With  flaming  torch  he  would  escort  pedestrians  to 
their  homes  on  dark  nights.  This  practice  was  in 
vogue  so  recently  that  the  “link-boy”  is  remembered 
by  persons  still  living.  In  England  the  profession  ap¬ 
pears  to  have  existed  until  about  1840. 

Somewhat  akin  to  the  wood-splinter,  and  a  forerun¬ 
ner  of  the  candle,  was  the  rushlight.  In  burning  wood 
man  noticed  that  a  resinous  or  fatty  material  increased 
the  inflammability  and  added  greatly  to  the  amount  of 
light  emitted.  It  was  a  logical  step  to  try  to  repro¬ 
duce  this  condition  by  artificial  means.  As  a  conse¬ 
quence  rushes  were  cut  and  soaked  in  water.  They 
were  then  peeled,  leaving  lengths  of  pith  partially  sup¬ 
ported  by  threads  of  the  skin  which  were  not  stripped 
off.  These  sticks  of  pith  were  placed  in  the  sun  to 
bleach  and  to  dry,  and  after  they  were  thoroughly 
dry  they  were  dipped  in  scalding  grease,  which  was 
saved  from  cooking  operations  or  was  otherwise  ac¬ 
quired  for  the  purpose.  A  reed  two  or  three  feet  long 
held  in  the  splinter-holder  would  burn  for  about  an 
hour.  Thus  it  is  seen  that  man  was  beginning  to  pro¬ 
gress  in  the  development  of  artificial  light.  In  devel- 


PRIMITIVE  LIGHT-SOURCES 


29 


oping  the  rushlight  he  was  laying  the  foundation  for 
the  invention  of  the  candle.  Pliny  has  mentioned  the 
burning  of  reeds  soaked  in  oil  as  a  feature  of  funeral 
rites.  Many  crude  forerunners  of  the  candle  were  de¬ 
veloped  in  various  parts  of  the  world  by  different  races. 
For  example,  the  Malays  made  a  torch  by  wrapping 
resinous  gum  in  palm  leaves,  thus  devising  a  crude 
candle  with  the  wick  on  the  outside. 

Many  primitive  uses  of  vegetable  and  animal  fats 
were  forerunners  of  the  oil-lamp.  In  the  East  Indies 
the  candleberry,  which  contains  oily  seeds,  has  been 
burned  for  light  by  the  natives.  In  many  cases  burn¬ 
ing  fish  and  birds  have  served  as  lamps.  In  the  Ork¬ 
ney  Islands  the  carcass  of  a  stormy  petrel  with  a  wick 
in  its  mouth  has  been  utilized  as  a  light-source,  and 
in  Alaska  a  fish  in  a  split  stick  has  provided  a  crude 
torch  for  the  natives.  These  primitive  methods  of  ob¬ 
taining  artificial  light  have  been  employed  for  cen¬ 
turies  and  many  are  in  use  at  the  present  time  among 
uncivilized  tribes  and  even  by  civilized  beings  in  the 
remote  outskirts  of  civilization.  Surely  progress  is 
limited  where  a  burning  fish  serves  as  a  torch,  or  where, 
at  best,  the  light-sources  are  feeble,  smoking,  flickering, 
and  ill-smelling ! 

Progress  insisted  upon  a  light-source  which  was  free 
from  the  defects  of  the  crude  devices  already  described 
and  the  next  developments  were  improvements  to  the 
extent  at  least  that  combustion  was  more  thorough. 
The  early  oil-lamps  and  candles  did  not  emit  much 
smoke,  but  they  were  still  feeble  light-sources  and  not 
always  without  noticeable  odors.  Nevertheless,  they 
marked  a  tremendous  advance  in  the  production  of  ar- 


30 


ARTIFICIAL  LIGHT 


tificial  light.  Although  they  were  not  scientific  devel¬ 
opments  in  the  modern  sense,  the  early  oil-lamp  and 
the  candle  represented  the  great  possibilities  of  utiliz¬ 
ing  knowledge  rather  than  depending  upon  the  raw 
products  of  nature  in  unmodified  forms.  The  advent 
of  these  two  light-sources  in  reality  marked  the  begin¬ 
ning  of  the  civilization  which  was  destined  to  progress 
and  survive. 

Although  such  primitive  light-sources  as  the  flaming 
splinter  and  the  glowing  ember  have  survived  until  the 
present  age,  lamps  consisting  of  a  wick  dipped  into  a 
receptacle  containing  animal  and  vegetable  oils  have 
been  in  use  among  the  more  advanced  peoples  since 
prehistoric  times.  Oil-lamps  are  to  be  seen  in  the 
earliest  Roman  illustrations.  During  the  height  of  an¬ 
cient  civilization  along  the  eastern  shores  of  the  Med¬ 
iterranean  Sea,  elaborate  lighting  was  effected  by 
means  of  the  shallow  grease-  or  oil-lamp.  It  is  diffi¬ 
cult  to  estimate  the  age  in  which  this  form  of  light- 
source  originated,  but  some  lamps  in  existence  in  col¬ 
lections  at  the  present  time  appear  to  have  been  made 
as  early  as  four  or  five  thousand  years  before  the 
Christian  era.  It  is  noteworthy  that  such  lamps  did 
not  differ  materially  in  essential  details  from  those  in 
use  as  late  as  a  few  centuries  ago. 

At  first  the  grease  used  was  the  crude  fat  from  ani¬ 
mals.  Vegetable  oils  also  were  burned  in  the  early 
lamps.  The  Japanese,  for  example,  extracted  oil  from 
nuts.  When  the  demands  of  civilization  increased,  ex¬ 
tensive  efforts  were  made  to  obtain  the  required  fats 
and  oils.  Amphibious  animals  of  the  North  and  the 
huge  mammals  of  the  sea  were  slaughtered  for  their 


PRIMITIVE  LIGHT-SOURCES  31 

fat,  and  vegetable  sources  were  cultivated.  Later, 
sperm  and  colza  were  the  most  common  oils  used  by 
the  advanced  races.  The  former  is  an  animal  oil  ob¬ 
tained  from  the  head  cavities  of  the  sperm-whale ;  the 
latter  is  a  vegetable  oil  obtained  from  rape-seed.  Min¬ 
eral  oil  was  introduced  as  an  illuminant  in  1853,  and 
the  modern  lamp  came  into  use. 

The  grease-  and  oil-lamps  in  general  were  of  such  a 
form  that  they  could  be  carried  with  ease  and  they  had 
flat  bottoms  so  that  they  would  rest  securely.  The 
simplest  forms  had  a  single  wick,  but  in  others  many 
wicks  dipped  into  the  same  receptacle.  The  early  ones 
were  of  stone,  but  later,  lamps  were  modeled  from 
clay  or  terra  cotta  and  finally  from  metals.  They 
were  usually  covered  and  the  wick  projected  through  a 
hole  in  the  top  near  the  edge.  Large  stone  vases  filled 
with  a  hundred  pounds  of  liquid  fat  are  known  to  have 
been  used  in  early  times.  As  a  part  of  the  setting  in 
the  celebration  of  festivals  the  ancient  nations  of  Asia 
and  Africa  placed  along  the  streets  bronze  vases  filled 
with  liquid  fat.  The  Esquimaux  to-day  use  this  form 
of  lamp,  in  which  whale-oil  and  seal  blubber  is  the  fuel. 
Incidentally,  these  lamps  also  supply  the  only  artificial 
heat  for  their  huts  and  igloos.  The  heat  from  these 
feeble  light-sources  and  from  their  bodies  keeps  these 
natives  of  the  arctics  warm  within  the  icy  walls  of 
their  abodes. 

Very  beautiful  oil-lamps  of  brass,  bronze,  and  pew¬ 
ter  evolved  in  such  countries  as  Egypt.  Many  of  these 
were  designed  for  and  used  in  religious  ceremonies. 
The  oil-lamps  of  China,  Scotland,  and  other  countries 
in  later  centuries  were  improved  by  the  addition  of  a 


32 


ARTIFICIAL  LIGHT 


pan  beneath  'the  oil-receptacle,  to  catch  drippings  from 
the  wick  or  oil  which  might  ran  over  during  the  tilling. 
The  Chinese  lamps  were  sometimes  made  of  bamboo, 
but  the  Scottish  lamps  were  made  of  metal.  A  flat 
metal  lamp,  called  a  crusie,  was  one  of  the  chief  prod¬ 
ucts  of  blacksmiths  and  was  common  in  Scotland  until 
the  middle  of  the  nineteenth  century.  This  type  of 
lamp  was  used  by  many  nations  and  has  been  found 
in  the  catacombs  of  Rome.  The  crusie  was  usually 
suspended  by  an  iron  hook  and  the  flow  of  oil  to  the 
wick  could  be  regulated  by  tilting.  The  wick  in  the 
Scottish  lamps  consisted  of  the  pith  of  rushes,  cloth, 
or  twis'ted  threads.  These  early  oil-lamps  were  al¬ 
most  always  shallow  vessels  into  which  a  short  wick 
was  dipped,  and  it  was  not  until  the  latter  part  of  the 
eighteenth  century  that  other  forms  came  into  gen¬ 
eral  use.  The  change  in  form  was  due  chiefly  to  the 
introduction  of  scientific  knowledge  when  mineral  oil 
was  introduced.  As  early  as  1781  the  burning  of  nap¬ 
tha  obtained  by  distilling  coal  at  low  temperatures  was 
first  discussed,  but  no  general  applications  were  made 
until  a  later  period.  This  was  the  beginning  of  many 
marked  improvements  in  oil-lamps,  and  was  in  reality 
the  birth  of  the  modern  science  of  light-production. 

As  the  activities  of  man  became  more  complex  he 
met  from  his  growing  store  of  knowledge  the  increas¬ 
ing  requirements  of  lighting.  In  consequence,  many 
ingenious  devices  for  lighting  were  evolved.  For  ex¬ 
ample,  in  England  in  the  seventeenth  century  man  was 
already  burrowing  into  the  earth  for  coal  and  of  course 
encountered  coal-gases.  These  inflammable  gases  were 
first  known  for  the  direful  effects  which  they  so  often 


A  TYPICAL  METAL  MULTIPLE-WICK  OPEN-FLAME  OIL-LAMP 


GROUP  OF  OIL-LAMPS  OF  TWO  CENTURIES  AGO 


PRIMITIVE  LIGHT-SOURCES 


33 


produced  rather  than  for  their  useful  qualities.  Al¬ 
though  they  were  known  to  miners  long  before  they 
received  scientific  attention,  the  earliest  account  of 
them  in  the  Transactions  of  the  Royal  Society  was 
presented  in  the  year  1667.  A  description  of  early  gas¬ 
lighting  has  been  reserved  for  a  later  chapter,  but  the 
foregoing  is  noted  at  this  point  to  introduce  a  novel 
early  method  of  lighting  in  coal-mines  where  inflam¬ 
mable  gases  were  encountered.  In  discussing  this 
coal-gas  another  early  writer  stated  that  “it  will  not 
take  fire  except  by  flame ’  ’  and  that  4 1  sparks  do  not  af¬ 
fect  it.”  One  of  the  early  solutions  of  the  problem 
of  artificial  lighting  under  such  conditions  is  summar¬ 
ized  as  follows : 

Before  the  invention  of  Sir  Humphrey  Davy’s 
Safety  Lamp,  this  property  of  the  gas  gave  rise  to  a 
variety  of  contrivances  for  affording  the  miners  suffi¬ 
cient  light  to  pursue  their  operations  ;  and  one  of  the 
most  useful  of  these  inventions  was  a  mill  for  pro¬ 
ducing  light  by  sparks  elicited  by  the  collision  of  flint 
and  steel. 

Such  a  stream  of  sparks  may  appear  a  very  crude  and 
unsatisfactory  solution  as  judged  by  present  stand¬ 
ards,  but  it  was  at  least  an  ingenious  application  of  the 
facilities  available  at  that  time.  Various  other  devices 
were  resorted  to  in  the  coal-mines  before  the  intro¬ 
duction  of  a  safety  lamp. 

In  discussing  the  candle  it  is  necessary  again  to  go 
back  to  an  early  period,  for  it  slowly  evolved  in  the 
course  of  many  centuries.  It  is  the  natural  descend¬ 
ant  of  the  rushlight,  the  grease-lamp,  and  various  prim¬ 
itive  devices.  Until  the  advent  of  the  more  scientific 


34 


ARTIFICIAL  LIGHT 


age  of  artificial  lighting,  the  candle  stood  preeminent 
among  early  light-sonrces.  It  did  not  emit  appreciable 
smoke  or  odor  and  it  was  cocnveniently  portable  and 
less  fragile  than  the  oil-lamp.  Candles  have  been  used 
throughout  the  Christian  era  and  some  authorities  are 
inclined  to  attribute  their  origin  to  the  Phoenicians. 
It  is  known  that  the  Romans  used  them,  especially  the 
wax-candles,  in  religious  ceremonies.  The  Phoenicians 
introduced  them  into  Byzantium,  but  they  disappeared 
under  the  Turkish  rule  and  did  not  come  into  use  again 
until  the  twelfth  century. 

The  wax-candle  was  very  much  more  expensive  than 
the  tallow-candle  until  the  fifteenth  century,  when  its 
relative  cost  was  somewhat  reduced,  bringing  it  within 
the  means  of  a  greater  proportion  of  the  people.  Nev¬ 
ertheless  it  has  long  been  used,  chiefly  by  the  wealthy ; 
the  departing  guest  of  the  early  Victorian  inn  would 
be  likely  to  find  an  item  on  his  bill  such  as  this :  “For 
a  gentleman  who  called  himself  a  gentleman,  wax- 
lights,  5/. ’  9  Poor  men  used  tallow  dips  or  went  to  bed 
in  the  dark.  It  is  interesting  to  note  the  importance  of 
the  candle  in  the  household  budget  of  early  times  in 
various  sayings.  For  example,  “The  game  is  not 
worth  the  candle,  ’  *  implies  that  the  cost  of  candle-light 
was  not  ignored.  In  these  days  little  attention  is 
given  to  the  cost  of  artificial  light  under  similar  condi¬ 
tions.  If  a  person  “burns  a  candle  at  both  ends”  he 
is  wasteful  and  oblivious  to  the  consequences  of  ex¬ 
travagance  whether  in  material  goods  or  in  human 
energy. 

With  the  rise  of  the  Christian  church,  candles  came 
to  be  used  in  religious  ceremonies  and  many  of  the 


PRIMITIVE  LIGHT-SOURCES 


35 


symbolisms,  meanings,  and  customs  survive  to  the 
present  time.  Some  of  the  finest  art  of  past  centuries 
is  found  in  the  old  candlesticks.  Many  of  these  an¬ 
tiques,  which  ofttimes  were  gifts  to  the  church,  have 
been  preserved  to  posterity  by  the  church.  The  influ¬ 
ence  of  these  lighting  accessories  is  often  noted  in  mod¬ 
em  lighting-fixtures,  but  unfortunately  early  art  often 
suffers  from  adaptation  to  the  requirements  of  modem 
light-sources,  or  the  eyesight  suffers  from  a  senseless 
devotion  to  art  which  results  in  the  use  of  modern  light- 
sources,  unshaded  and  glaring,  in  places  where  it  was 
unnecessary  to  shade  the  feeble  candle. 

The  oldest  materials  employed  for  making  candles 
are  beeswax  and  tallow.  The  beeswax  was  bleached 
before  use.  The  tallow  was  melted  and  strained  and 
then  cotton  or  flax  fibers  were  dipped  into  it  repeat¬ 
edly,  until  the  desired  thickness  was  obtained.  In 
early  centuries  the  pith  of  rushes  was  used  for  wicks. 
Tallow  is  now  used  only  as  a  source  of  stearine.  Sper¬ 
maceti,  a  fatty  substance  obtained  from  the  sperm- 
whale,  was  introduced  into  candle-making  in  about  1750 
and  great  numbers  of  men  searched  the  sea  to  fill  the 
growing  demands.  Paraffin  wax,  a  mixture  of  solid 
hydrocarbons  obtained  from  petroleum,  came  into  use 
in  1854  and  stearine  is  now  used  with  it.  The  latter 
increases  the  rigidity  and  decreases  the  brittleness  of 
the  candle.  Some  of  the  modern  candles  are  made  of 
a  mixture  of  stearine  and  the  hard  fat  extracted  from 
cocoanut-oil.  Modern  candles  vary  in  composition,  but 
all  are  the  product  of  much  experience  and  of  the  ap¬ 
plication  of  scientific  knowledge.  The  wicks  are  now 
made  chiefly  of  cotton  yarn,  braided  or  plaited  by  ma- 


36 


ARTIFICIAL  LIGHT 


chinery  and  chemically  treated  to  aid  in  complete  com¬ 
bustion  when  the  candle  is  burned.  Their  structure 
is  the  result  of  long  experience  and  they  are  now  made 
so  that  they  bend  and  dip  into  the  molten  fuel  and 
are  wholly  consumed.  This  eliminates  the  necessity 
of  trimming. 

Candles  have  been  made  in  various  ways,  including 
dipping,  pouring,  drawing,  and  molding.  Wax-can¬ 
dles  are  made  by  pouring,  because  wax  cannot  be 
molded  satisfactorily.  Drawing  is  somewhat  similar 
to  dipping,  except  that  the  process  is  more  or  less  con¬ 
tinuous  and  is  carried  out  by  machinery.  Molding,  as 
the  term  implies,  involves  the  use  of  molds,  of  the  size 
and  shape  desired. 

The  candlestick  evolved  from  the  most  primitive 
wooden  objects  to  elaborately  designed  and  decorated 
works  of  art.  The  primitive  candlestick  was  crude 
and  was  no  more  than  a  holder  of  some  kind  for  keep¬ 
ing  the  candle  upright.  Later  a  form  of  cup  was  at¬ 
tached  to  the  stem  of  the  holder,  to  catch  the  dripping 
wax  or  fat.  The  latter  improvement  has  persisted 
throughout  the  centuries.  The  modern  candle  is  by  no 
means  an  unsatisfactory  light-source.  Those  who  have 
had  experience  with  it  in  the  outskirts  of  civilization 
will  testify  that  it  possesses  several  desirable  char¬ 
acteristics.  Supplies  of  candles  are  transported  with¬ 
out  difficulty ;  the  lighted  candle  is  easily  carried  about ; 
and  the  light  in  a  quiescent  atmosphere  is  quite  satis¬ 
factory,  if  common  sense  is  used  in  shading  and  plac¬ 
ing  the  candle.  Although  in  a  sense  a  primitive  light- 
source,  it  is  a  blessing  in  many  cases  and,  incidentally, 
it  is  extensively  used  to-day  in  industries,  in  religious 


PRIMITIVE  LIGHT-SOURCES  87 

ceremonies,  as  a  decorative  element  at  banquets,  and 
in  the  outposts  of  civilization. 

This  account  of  the  evolution  of  light-sources  has 
crossed  the  threshold  of  what  may  be  termed  modern 
scientific  light -production  in  the  case  of  the  candle  and 
the  oil-lamp.  There  is  a  period  of  a  century  or  more 
during  which  scientific  progress  was  slow,  but  those 
years  paved  the  way  for  the  extraordinary  develop¬ 
ments  of  the  last  few  decades. 


IV 

* 

THE  CEREMONIAL  USE  OF  LIGHT 

Inasmuch  as  the  symbolisms  and  ceremonial  uses  of 
light  originated  in  the  childhood  of  the  human  race  and 
were  nourished  throughout  the  age  of  mythology,  the 
early  light-sources  are  associated  more  with  this  phase 
of  artificial  light  than  modern  ones.  For  this  reason 
it  appears  appropriate  to  present  this  discussion  be¬ 
fore  entering  into  the  later  stages  of  the  development 
and  utilization  of  artificial  light.  Furthermore,  many 
of  the  traditions  of  lighting  at  the  present  time  are  sur¬ 
vivors  of  the  early  ages.  Lighting-fixtures  show  the 
influence  of  this  byway  of  lighting,  and  in  those  cases 
where  the  ceremonial  use  of  light  has  survived  to  the 
present  time,  modern  light-sources  cannot  be  employed 
wisely  in  replacing  more  primitive  ones  without  con¬ 
sideration  of  the  origin  and  existence  of  the  customs. 
In  fact,  candles  are  likely  to  be  used  for  hundreds  of 
years  to  come,  owing  to  the  sentiment  connected  with 
them  and  to  the  established  customs  founded  upon  cen¬ 
turies  of  traditional  use. 

Doubtless,  the  sun  as  a  source  of  heat  and  light  and 
of  the  blessings  which  these  bring  to  earth,  is  responsi¬ 
ble  largely  for  the  divine  significance  bestowed  upon 
light.  Darkness  very  deservingly  acquired  many  un¬ 
complimentary  attributes,  for  danger  lurked  behind  its 
veil  and  it  was  the  suitable  abode  of  evil  spirits.  It 

38 


THE  CEREMONIAL  USE  OF  LIGHT  39 


harbored  all  that  was  the  antithesis  of  goodness,  hap¬ 
piness,  and  security.  Light  naturally  became  sacred, 
life-giving,  and  symbolic  of  divine  presence.  Fire  was 
to  primitive  beings  the  most  impressive  phenomenon 
over  which  they  had  any  control,  and  it  was  sufficiently 
mysterious  in  its  operation  to  warrant  a  connection 
with  the  supernatural.  Thus  it  was  very  natural  that 
these  earlier  beings  worshiped  it  as  representing  divine 
presence.  The  sun,  as  Ra,  was  one  of  the  chief  gods 
of  the  ancient  Egyptians ;  and  the  Assyrians,  the  Baby¬ 
lonians,  the  ancient  Greeks,  and  many  other  early  peo¬ 
ples  gave  a  high  place  to  this  deity.  Among  simpler 
races  the  sun  was  often  the  sole  object  of  worship,  and 
those  peoples  who  worship  Light  as  the  god  of  all,  in  a 
sense  are  not  far  afield.  Fire-worshipers  generally 
considered  fire  as  the  purest  representation  of  heavenly 
fire,  the  origin  of  everything  that  lives. 

Light  was  considered  such  a  blessing  that  lamps  were 
buried  with  the  dead  in  order  that  spirits  should  be 
able  to  have  it  in  the  next  world.  This  custom  has 
prevailed  widely  but  the  fact  that  the  lamps  were  un¬ 
lighted  indicates  that  only  the  material  aspect  was 
considered.  It  is  interesting  to  note  that  the  lamps 
and  other  light-sources  in  pagan  temples  and  religious 
processions  were  not  symbolical  but  were  offerings  to 
the  gods.  In  later  centuries  a  deeper  symbolical  mean¬ 
ing  became  attached  to  light  and  burning  lamps  were 
placed  upon  the  tombs  of  important  personages.  The 
burying  of  lamps  with  the  dead  appears  to  have  orig¬ 
inated  in  Asia.  The  Phoenicians  and  Romans  appar¬ 
ently  continued  the  custom,  but  no  traces  of  it  have 
been  found  in  Greece  and  Egypt. 


40 


ARTIFICIAL  LIGHT 


Fire  and  light  have  been  closely  associated  in  va¬ 
rious  religious  creeds  and  their  ceremonies.  The 
Hindu  festival  in  honor  of  the  goddess  of  prosperity 
is  attended  by  the  burning  of  many  lamps  in  the  tem¬ 
ples  and  homes.  The  Jewish  synagogues  have  their 
eternal  lamps  and  in  their  rituals  fire  and  light  have 
played  prominent  roles.  The  devout  Brahman  main¬ 
tains  a  fire  on  the  hearth  and  worships  it  as  omnis¬ 
cient  and  divine.  He  expects  a  brand  from  this  to  be 
used  to  light  his  funeral  pyre,  whose  fire  and  light 
will  make  his  spirit  fit  to  enter  his  heavenly  abode. 
He  keeps  a  fire  burning  on  the  altar,  worships  Agni, 
the  god  of  fire,  and  makes  fire  sacrifices  on  various 
occasions  such  as  betrothals  and  marriages.  To  the 
Mohammedans  lighted  lamps  symbolize  holy  places, 
and  the  Kaaba  at  Mecca,  which  contains  a  black  stone 
supposed  to  have  been  brought  from  heaven,  is  illum¬ 
inated  by  thousands  of  lamps.  Many  of  the  uses  to 
which  light  was  put  in  ancient  times  indicate  its  rarity 
and  sacred  nature.  Doubtless,  the  increasing  use  of 
artificial  light  at  festivals  and  celebrations  of  the  pres¬ 
ent  time  is  partly  the  result  of  lingering  customs  of 
bygone  centuries  and  partly  due  to  a  recognition  of 
an  innate  appeal  or  attribute  of  light.  Certainly  noth¬ 
ing  is  more  generally  appropriate  in  representing  joy 
and  prosperity. 

Throughout  all  countries  ancient  races  had  woven 
natural  light  and  fire  into  their  rites  and  customs,  so 
it  became  a  natural  step  to  utilize  artificial  light  and 
fire  in  the  same  manner.  It  would  be  tedious  and  mo¬ 
notonous  to  survey  the  vast  field  of  ancient  worship 
of  light,  for  the  underlying  ideas  are  generally  simi- 


THE  CEREMONIAL  USE  OF  LIGHT  41 


lar.  The  mythology  of  the  Greeks  is  illustrative  of 
the  importance  attached  to  fire  and  light  by  the  culti¬ 
vated  peoples  of  ancient  times.  The  myth  of  Prome¬ 
theus  emphasizes  the  fact  that  in  those  remote  pe¬ 
riods  fire  and  light  were  regarded  as  of  prime  impor¬ 
tance.  According  to  this  myth,  fire  and  light  were  con¬ 
tained  in  heaven  and  great  cunning  and  daring  were 
necessary  in  order  to  obtain  it.  Prometheus  stole  this 
heavenly  fire,  for  which  act  he  was  chained  to  the  moun¬ 
tain  and  made  to  suffer.  The  Greeks  mark  this  event 
as  the  beginning  of  human  civilization.  All  arts  are 
traced  to  Prometheus,  and  all  earthly  woe  likewise. 
As  past  history  is  surveyed  it  appears  natural  to  think 
of  scientific  men  who  have  become  martyrs  to  the  quest 
of  hidden  secrets.  They  have  made  great  sacrifices  for 
the  future  benefit  of  civilization  and  not  a  few  of  them 
have  endured  persecution  even  in  recent  times.  The 
Greeks  recognized  that  a  new  era  began  with  the  acqui¬ 
sition  of  artificial  light.  Its  divine  nature  was  recog¬ 
nized  and  it  became  a  phenomenon  for  worship  and  a 
means  for  representing  divine  presence.  The  origin 
of  fire  and  light  made  them  holy.  The  fire  on  the  al¬ 
tar  took  its  place  in  religious  rites  and  there  evolved 
many  ceremonial  uses  of  lamps,  candles,  and  fire. 

The  Greeks  and  Romans  burned  sacred  lamps  in 
the  temples  and  utilized  light  and  fire  in  many  cere¬ 
monies.  The  torch-race,  in  which  young  men  ran  with 
lighted  torches,  the  winner  being  the  one  who  reached 
the  goal  first  with  his  torch  still  alight,  originated  in  a 
Grecian  ceremony  of  lighting  the  sacred  fire.  There 
are  many  references  in  ancient  Roman  and  Grecian  lit¬ 
erature  to  sacred  lamps  burning  day  and  night  in  sane- 


42 


ARTIFICIAL  LIGHT 


tuaries  and  before  statues  of  gods  and  heroes.  On 
birthdays  and  festivals  the  houses  of  the  Romans  were 
specially  ornamented  with  burning  lamps.  The  Vestal 
Virgins  in  Rome  maintained  the  sacred  fire  which  had 
been  brought  by  fugitives  from  Troy.  In  ancient  Rome 
when  the  fire  in  the  Temple  of  Vesta  became  extin¬ 
guished,  it  was  rekindled  by  the  rubbing  of  a  piece  of 
wood  upon  another  until  fire  was  obtained.  This  was 
carried  into  the  temple  by  the  Vestal  Virgin  and  the 
sacred  fire  was  rekindled.  The  fire  produced  in  this 
manner,  for  some  reason,  was  considered  holy. 

The  early  peoples  displayed  many  lamps  on  feast- 
days  and  an  example  of  extravagance  in  this  respect 
is  an  occasion  when  King  Constantine  commanded  that 
the  entire  city  of  Constantinople  be  illuminated  by  wax- 
candles  on  Christmas  Eve.  Candelabra,  of  the  form 
of  the  branching  tree,  were  commonly  in  use  in  the 
Roman  temples. 

The  ceremonial  use  of  light  in  the  Christian  church 
evolved  both  from  adaptations  of  pagan  customs  and 
of  the  natural  symbolisms  of  fire  and  light.  However, 
these  acquired  a  deeper  meaning  in  Christianity  than 
in  early  times  because  they  were  primarily  visible  rep¬ 
resentations  or  manifestations  of  the  divine  presence. 
The  Bible  contains  many  references  to  the  importance 
and  symbolisms  of  light  and  fire.  According  to  the 
First  Book  of  Moses,  the  achievement  of  the  Creator 
immediately  following  the  creation  of  4  4  the  heavens  and 
the  earth  ”  was  the  creation  of  light.  The  word 
“light”  is  the  forty-sixth  word  in  Genesis.  Christ  is 
“the  true  light”  and  Christians  are  “children  of  light” 
in  war  against  the  evil  “powers  of  darkness.”  When 


THE  CEREMONIAL  USE  OF  LIGHT  43 

St.  Paul  was  converted  "  there  shined  about  him  a 
great  light  from  heaven.  ”  The  impressiveness  and 
symbolism  of  tire  and  light  are  testified  to  in  many 
biblical  expressions.  Christ  stands  "in  the  midst  of 
seven  candle-sticks ? ’  with  "his  eyes  as  a  flame  of  fire.” 
When  the  Holy  Ghost  appeared  before  the  apostles 
"there  appeared  unto  them  cloven  tongues  of  fire.” 
When  St.  Paul  was  preaching  the  gospel  of  Christ  at 
Alexandria  "there  were  many  lights”  suggesting  a 
festive  illumination. 

According  to  the  Bible,  the  perpetual  fire  which  came 
originally  from  heaven  was  to  be  kept  burning  on  the 
altar.  It  was  holy  and  those  whose  duty  it  was  to  keep 
it  burning  were  guilty  of  a  grave  offense  if  they  al¬ 
lowed  it  to  be  extinguished.  If  human  hands  were  per¬ 
mitted  to  kindle  it,  punishment  was  meted  out.  The 
two  sons  of  Aaron  who  "offered  strange  fire  before 
the  Lord”  were  devoured  by  "fire  from  the  Lord.” 
The  seven-branched  candlestick  was  lighted  eternally 
and  these  burning  light-sources  were  necessary  accom¬ 
paniments  of  worship. 

The  countless  ceremonial  uses  of  fire  and  light  which 
had  evolved  in  the  past  centuries  were  bound  to  influ¬ 
ence  the  rites  and  customs  of  the  Christian  church. 
The  festive  illumination  of  pagan  temples  in  honor  of 
gods  was  carried  over  into  the  Christian  era.  The 
Christmas  tree  of  to-day  is  incomplete  without  its  many 
lights.  Its  illumination  is  a  homage  of  light  to  the 
source  of  light.  The  celebration  of  Easter  in  the 
Church  of  the  Holy  Sepulchre  in  Jerusalem  is  a  typi¬ 
cal  example  of  fire-worship  retained  from  ancient  times. 
At  the  climax  of  the  services  comes  the  descent  of  the 


44 


ARTIFICIAL  LIGHT 


Holy  Fire.  The  central  candelabra  suddenly  becomes 
ablaze  and  the  worshipers,  each  of  whom  carries  a  wax 
taper,  light  their  candles  therefrom  and  rush  through 
the  streets.  The  fire  is  considered  to  be  of  divine  ori¬ 
gin  and  is  a  symbol  of  resurrection.  The  custom  is 
similar  in  meaning  to  the  light  which  in  older  times 
was  maintained  before  gods. 

During  the  first  two  or  three  centuries  of  the  Chris¬ 
tian  era  the  ceremonial  use  of  light  does  not  appear  to 
have  been  very  extensive.  Writings  of  the  period  con¬ 
tain  statements  which  appear  to  ridicule  this  use  to 
some  extent.  For  example,  one  writer  of  the  second 
century  states  that  “On  days  of  rejoicing  ...  we  do 
not  encroach  upon  daylight  with  lamps.”  Another,  in 
the  fourth  century,  refers  with  sarcasm  to  the  “heathen 
practice”  in  this  manner:  “They  kindle  lights  as 
though  to  one  who  is  in  darkness.  Can  he  be  thought 
sane  who  offers  the  light  of  lamps  and  candles  to  the 
Author  and  Giver  of  all  light?” 

That  candles  were  lighted  in  cemeteries  is  evidenced 
by  an  edict  which  forbade  their  use  during  the  day. 
Lamps  of  the  early  centuries  of  the  Christian  era  have 
been  found  in  the  catacombs  of  Rome  which  are  thought 
to  have  been  ceremonial  lamps,  for  they  were  not 
buried  with  the  dead.  They  were  found  only  in  niches 
in  the  walls.  During  these  same  centuries  elaborate 
candelabra  containing  hundreds  of  candles  were  kept 
burning  before  the  tombs  of  saints.  Notwithstanding 
the  doubt  that  exists  as  to  the  extent  of  ceremonial 
lighting  in  the  early  centuries  of  the  Christian  era,  it 
is  certain  that  by  the  beginning  of  the  fifth  century 
the  ceremonial  use  of  light  in  the  Christian  church  had 


THE  CEREMONIAL  USE  OF  LIGHT  45 


become  very  extensive  and  firmly  established.  That 
this  is  true  and  that  there  were  still  some  objections  is 
indicated  by  many  controversies.  Some  thought  that 
lamps  before  tombs  were  ensigns  of  idolatry  and  others 
felt  that  no  harm  was  done  if  religious  people  thus 
tried  to  honor  martyrs  and  saints.  Some  early  writ¬ 
ings  convey  the  idea  that  the  ritualistic  use  of  lights  in 
the  church  arose  from  the  retention  of  lights  necessary 
at  nocturnal  services  after  the  hours  of  worship  had 
been  changed  to  daytime. 

Passing  beyond  the  early  controversial  period,  the 
ceremonial  use  of  light  is  everywhere  in  evidence  at 
ordinary  church  services.  On  special  occasions  such 
as  funerals,  baptisms,  and  marriages,  elaborate  altar¬ 
lighting  was  customary.  The  gorgeous  candelabra  and 
the  eternal  lamp  are  noted  in  many  writings.  Early  in 
the  fifth  century  the  pope  ordered  that  candles  be 
blessed  and  provided  rituals  for  this  ceremony. 
Shortly  after  this  the  Feast  of  Purification  of  the  Vir¬ 
gin  was.  inaugurated  and  it  became  known  as  Candle¬ 
mas  because  on  this  day  the  candles  for  the  entire  year 
were  blessed.  However,  it  appears  that  the  blessing  of 
candles  was  not  carried  out  in  all  churches.  Altar 
lights  were  not  generally  used  until  the  thirteenth  cen¬ 
tury.  They  were  originally  the  seven  candles  carried 
by  church  officials  and  placed  near  the  altar. 

The  custom  of  placing  lighted  lamps  before  the  tombs 
of  martyrs  was  gradually  extended  to  the  placing  of 
such  lamps  before  various  objects  of  a  sacred  or  di¬ 
vine  relation.  Finally  certain  light-sources  themselves 
became  objects  of  worship  and  were  surrounded  by 
other  lamps,  and  the  symbolisms  of  light  grew  apace. 


46 


ARTIFICIAL  LIGHT 


A  bishop  in  the  sixth  century  heralded  the  triple  offer¬ 
ing  to  God  represented  by  the  burning  wax-candle. 
He  pointed  out  that  the  rush-wick  developed  from  pure 
water;  that  the  wax  was  the  product  of  virgin  bees; 
and  that  the  flame  was  sent  from  heaven.  Each  of 
these,  he  was  certain,  was  an  offering  acceptable  to 
God.  Wax-candles  became  associated  chiefly  with  re¬ 
ligious  ceremonies.  The  wax  later  became  symbolic  of 
the  Blessed  Virgin  and  of  the  body  of  Christ.  The 
wick  was  symbolical  of  Christ’s  soul,  the  flame  repre¬ 
sented  his  divine  character,  and  the  burning  candle  thus 
became  symbolical  of  his  death.  The  lamp,  lantern, 
and  taper  are  frequently  symbols  of  piety,  heavenly 
wisdom,  or  spiritual  light.  Fire  and  flames  are  em¬ 
blems  of  zeal  and  fervor  or  of  the  sufferings  of  martyr¬ 
dom  and  the  flaming  heart  symbolizes  fervent  piety  and 
spiritual  or  divine  love. 

By  the  time  the  Middle  Ages  were  reached  the  cere¬ 
monial  uses  of  light  became  very  complex,  but  for  the 
Roman  Catholic  Church  they  may  be  divided  into  three 
general  groups:  (1)  They  were  symbolical  of  God’s 
presence  or  of  the  effect  of  his  presence;  of  Christ  or 
of  4 4 the  children  of  light”;  or  of  joy  and  content  at 
festivals.  (2)  They  may  be  offered  in  fulfillment  of  a 
religious  vow;  that  is,  as  an  act  of  worship.  (3)  They 
may  possess  certain  divine  power  because  of  their  be¬ 
ing  blessed  by  the  church,  and  therefore  may  be  help¬ 
ful  to  soul  and  body.  The  three  conceptions  are  indi¬ 
cated  in  the  prayers  offered  at  the  blessing  of  the  can¬ 
dles  on  Candlemas  as  follows:  (1)  “0  holy  Lord  .  .  . 
who  ...  by  thy  command  didst  cause  this  liquid  to 
come  by  the  labor  of  bees  to  the  perfection  of  wax,  .  .  . 


THE  CEREMONIAL  USE  OF  LIGHT  47 


we  beseech  thee  ...  to  bless  and  sanctify  these  can¬ 
dles  for  the  use  of  men,  and  the  health  of  bodies  and 
souls.  ...”  (2)  .  .  these  candles,  which  we  thy 

servants  desire  to  carry  lighted  to  magnify  thy  name ; 
that  by  offering  them  to  thee,  being  worthily  inflamed 
with  the  holy  fire  of  thy  most  sweet  charity,  we  may 
deserve.  .  .  .  ”  (3)  “0  Lord  Jesus  Christ,  the  true 

light,  .  .  .  mercifully  grant,  that  as  these  lights  en¬ 
kindled  with  visible  fire  dispel  nocturnal  darkness,  so 
our  hearts  illuminated  by  visible  fire,”  etc. 

In  general,  the  ceremonial  uses  of  lights  in  this 
church  were  originated  as  a  forceful  representation  of 
Christ  and  of  salvation.  On  the  eve  of  Easter  a  new 
fire,  emblematic  of  the  arisen  Christ,  is  kindled,  and 
all  candles  throughout  the  year  are  lighted  from  this. 
During  the  service  of  Holy  Week  thirteen  lighted  can¬ 
dles  are  placed  before  the  altar  and  as  the  penitential 
songs  are  sung  they  are  extinguished  one  by  one. 
When  but  one  remains  burning  it  is  carried  behind  the 
altar,  thus  symbolizing  the  last  days  of  Christ  on  earth. 
It  is  said  that  this  ceremony  has  been  traced  to  the 
eighth  century.  On  Easter  Eve,  after  the  new  fire  is 
lighted  and  blessed,  certain  ceremonies  of  light  sym¬ 
bolize  the  resurrection  of  Christ.  From  this  new  fire 
three  candles  are  lighted  and  from  these  the  Paschal 
Candle.  The  origin  of  the  latter  is  uncertain,  but  it 
symbolizes  a  victorious  Christ.  From  it  all  the  cere¬ 
monial  lights  of  the  church  are  lighted  and  they  thereby 
are  emblematic  of  the  presence  of  the  light  of  Christ. 

Many  interesting  ceremonial  uses  may  be  traced  out, 
but  space  permits  a  glimpse  of  only  a  few.  At  bap¬ 
tismal  services  the  paschal  candle  is  dipped  into  the 


48 


ARTIFICIAL  LIGHT 


water  so  that  the  latter  will  be  effective  as  a  regenera¬ 
tive  element.  The  baptized  child  is  reborn  as  a  child 
of  light.  Lighted  candles  are  placed  in  the  hands  of 
the  baptized  persons  or  of  their  god-parents.  Those 
about  to  take  vows  carry  lights  before  the  church  offi¬ 
cial  and  the  same  idea  is  attached  to  the  custom  of 
carrying  or  of  holding  lights  on  other  occasions  such 
as  weddings  and  first  communion.  Lights  are  placed 
around  the  bodies  of  the  dead  and  are  carried  at  the 
funeral.  They  not  only  protect  the  dead  from  the 
powers  of  darkness  but  they  symbolize  the  dead  as 
still  living  in  the  light  of  Christ.  The  use  of  lighted 
candles  around  bodies  of  the  dead  still  survives  to  some 
extent  among  Protestants,  but  their  significance  has 
been  lost  sight  of.  Even  in  the  eighteenth  century 
funerals  in  England  were  accompanied  by  lighted  ta¬ 
pers,  but  the  carrying  of  lights  in  other  processions  ap¬ 
pears  to  have  ceased  with  the  Reformation.  In  some 
parts  of  Scotland  it  is  still  the  custom  to  place  two 
lighted  candles  on  a  table  beside  a  corpse  on  the  day 
of  the  funeral. 

With  the  importance  of  light  in  the  ritual  of  the 
church  it  is  not  surprising  that  the  extinction  of  lights 
is  a  part  of  the  ceremony  of  excommunication.  Such 
a  ceremony  is  described  in  an  early  writing  thus: 
“Twelve  priests  should  stand  about  the  bishop,  holding 
in  their  hands  lighted  torches,  which  at  the  conclusion 
of  the  anathema  or  excommunication  they  should  cast 
down  and  trample  under  foot.  ’  ’  When  the  excommuni¬ 
cant  is  reinstated,  a  lighted  candle  is  placed  in  his 
hands  as  a  symbol  of  reconciliation.  These  and  many 


THE  CEREMONIAL  USE  OF  LIGHT  49 

other  ceremonial  uses  of  light  have  been  and  are  prac¬ 
tised,  but  they  are  not  always  mandatory.  Further¬ 
more,  the  customs  have  varied  from  time  to  time,  but 
the  few  which  have  been  touched  upon  illustrate  the 
impressive  part  that  light  has  played  in  religious 
services. 

During  the  Reformation  the  ceremonial  use  of  lights 
was  greatly  altered  and  was  abolished  in  the  Protestant 
churches  as  a  relic  of  superstition  and  papal  authority. 
In  the  Lutheran  churches  ceremonial  lights  were 
largely  retained,  in  the  Church  of  England  they  have 
been  subjected  to  many  changes  largely  through  the 
edicts  of  the  rulers.  In  the  latter  church  many  contro¬ 
versies  were  waged  over  ceremonial  lights  and  their 
use  has  been  among  the  indictments  of  a  number  of 
officials  of  the  church  in  impeachment  cases  before  the 
House  of  Commons.  Many  uses  of  light  in  religious 
ceremonies  were  revived  in  cathedrals  after  the  Res¬ 
toration  and  they  became  wide-spread  in  England  in 
the  nineteenth  century.  As  late  as  1889  the  Arch¬ 
bishop  of  Canterbury  ruled  that  certain  ceremonial 
candles  were  lawful  according  to  the  Prayer-Book  of 
Edward  VI,  but  the  whole  question  was  left  open  and 
unsettled. 

These  byways  of  artificial  light  are  complex  and  fas¬ 
cinating  because  their  study  leads  into  many  channels 
and  far  into  the  obscurity  of  the  childhood  of  the  hu¬ 
man  race.  A  glimpse  of  them  is  important  in  a  sur¬ 
vey  of  the  influence  of  artificial  light  upon  the  progress 
of  civilization  because  in  these  usages  the  innate  and 
acquired  impressiveness  of  light  is  encountered.  Al- 


50 


ARTIFICIAL  LIGHT 


though  many  ceremonial  uses  of  light  remain,  it  is 
doubtful  if  their  significance  and  especially  their  ori¬ 
gin  are  appreciated  by  most  persons.  Nevertheless, 
no  more  interesting  phase  of  artificial  light  is  encount¬ 
ered  than  this,  which  reaches  to  the  foundation  of 
civilization. 


V 

OIL-LAMPS  OF  THE  NINETEENTH  CENTURY 

It  will  be  noted  that  the  light-sonrces  throughout  the 
early  ages  were  flames,  the  result  of  burning  material. 
This  principle  of  light-production  has  persisted  until 
the  present  time,  but  in  the  latter  part  of  the  nineteenth 
century  certain  departures  revolutionized  artificial 
lighting.  However,  it  is  not  the  intention  to  enter  the 
modern  period  in  this  chapter  except  in  following  the 
progress  of  the  oil-lamp  through  its  period  of  scien¬ 
tific  development.  The  oil-lamp  and  the  candle  were 
the  mainstays  of  artificial  lighting  throughout  many 
centuries.  The  fats  and  waxes  which  these  light- 
sources  burned  were  many  but  in  the  later  centuries 
they  were  chiefly  tallow,  sperm-oil,  spermaceti,  lard-oil, 
olive-oil,  colza-oil,  bees-wax  and  vegetable  waxes. 
Those  fuels  which  are  not  liquid  are  melted  to  liquid 
form  by  the  heat  of  the  flame  before  they  are  actually 
consumed.  The  candle  is  of  the  latter  type  and  despite 
its  present  lowly  place  and  its  primitive  character,  it 
is  really  an  ingenious  device.  Its  fuel  remains  con¬ 
veniently  solid  so  that  it  is  readily  shipped  and  stored; 
there  is  nothing  to  spill  or  to  break  beyond  easy  re¬ 
pair;  but  when  it  is  lighted  the  heat  of  its  flame  melts 
the  solid  fuel  and  thus  it  becomes  an  ‘  ‘  oil-lamp.  ’ ’  Ani¬ 
mal  and  vegetable  oils  were  mainly  used  until  the  mid¬ 
dle  of  the  nineteenth  century,  when  petroleum  was  pro- 

51 


52 


ARTIFICIAL  LIGHT 


duced  in  sufficient  quantities  to  introduce  mineral  oils. 
This  marked  the  beginning  of  an  era  of  developments 
in  oil-lamps,  but  these  were  generally  the  natural  off¬ 
spring  of  early  developments  by  Ami  Argand. 

Before  man  discovered  that  nature  had  stored  a  tre¬ 
mendous  supply  of  mineral  oil  in  the  earth  he  was 
obliged  to  hunt  broadcast  for  fats  and  waxes  to  sup¬ 
ply  him  with  artificial  light.  He  also  was  obliged  to 
endure  unpleasant  odors  from  the  crude  fuels  and  in 
early  experiments  with  fats  and  waxes  the  odor  was 
carefully  noted  as  an  important  factor.  Tallow  was  a 
by-product  of  the  kitchen  or  of  the  butcher.  Stearine, 
a  constituent  of  tallow,  is  a  compound  of  glyceryl  and 
stearic  acid.  It  is  obtained  by  breaking  up  chemically 
the  glycerides  of  animal  fats  and  separating  the  fatty 
acids  from  glycerin.  Fats  are  glycerides ;  that  is,  com¬ 
binations  of  oleic,  palmetic,  and  stearic  acids.  Inas¬ 
much  as  the  former  is  liquid  at  ordinary  temperatures 
and  the  others  are  solid,  it  follows  that  the  consistency 
or  solidity  of  fats  depends  upon  the  relative  propor¬ 
tions  of  the  three  constituents.  The  sperm-whale, 
which  lives  in  the  warmer  parts  of  all  the  oceans,  has 
been  hunted  relentlessly  for  fuels  for  artificial  light¬ 
ing.  In  its  head  cavities  sperm-oil  in  liquid  form  is 
found  with  the  white  waxy  substance  known  as  sper¬ 
maceti.  Colza-oil  is  yielded  by  rape-seed  and  olive-oil 
is  extracted  from  ripe  olives.  The  waxes  are  combina¬ 
tions  of  allied  acids  with  bases  somewhat  related  to 
glycerin  but  of  complex  composition.  Fats  and  waxes 
are  more  or  less  related,  but  to  distinguish  them  care¬ 
fully  would  lead  far  afield  into  the  complexities  of  or¬ 
ganic  chemistry.  All  these  animal  and  vegetable  prod- 


OIL-LAMPS 


53 


ucts  which  were  used  as  fuels  for  light-sources  are 
rich  in  carbon,  which  accounts  for  the  light-value  of 
their  flames.  The  brightness  of  such  a  flame  is  due 
to  incandescent  carbon  particles,  but  this  phase  of  light- 
production  is  discussed  in  another  chapter.  These  oils, 
fats,  and  waxes  are  composed  by  weight  of  about  75 
to  80  per  cent,  carbon;  10  to  15  per  cent,  hydrogen; 
and  5  to  10  per  cent,  oxygen. 

Until  the  middle  of  the  eighteenth  century  the  oil- 
lamps  were  shallow  vessels  filled  with  animal  or  veg¬ 
etable  oil  and  from  these  reservoirs  short  wicks  pro¬ 
jected.  The  flame  was  feeble  and  smoky  and  the  odors 
were  sometimes  very  repugnant.  Viewing  such  light- 
sources  from  the  present  age  in  which  light  is  plentiful, 
convenient,  and  free  from  the  great  disadvantages  of 
these  early  oil-lamps,  it  is  difficult  to  imagine  the  possi¬ 
bility  of  the  present  civilization  emerging  from  that 
period  without  being  accompanied  by  progress  in  light- 
production.  The  improvements  made  in  the  eight¬ 
eenth  century  paved  the  way  for  greater  progress  in 
the  following  century.  This  is  the  case  throughout 
the  ages,  but  there  are  special  reasons  for  the  tre¬ 
mendous  impetus  which  light-production  has  expe¬ 
rienced  in  the  past  half-century.  These  are  the  ac¬ 
quirement  of  scientific  knowledge  from  systematic  re¬ 
search  and  the  application  of  this  knowledge  by  or¬ 
ganized  development. 

The  first  and  most  notable  improvement  in  the  oil- 
lamp  was  made  by  Argand  in  1784.  Our  nation  was 
just  organizing  after  its  successful  struggle  for  inde¬ 
pendence  at  the  time  when  the  production  of  light  as  a 
science  was  born.  Argand  produced  the  tubular  wick 


54 


ABTIFICIAL  LIGHT 


and  contributed  the  greatest  improvement  by  being  the 
first  to  perform  the  apparently  simple  act  of  placing 
a  glass  chimney  upon  the  lamp.  His  burner  consisted 
of  two  concentric  metal  tubes  between  which  the  wick 
was  located.  The  inner  tube  was  open,  so  that  air 
could  reach  the  inner  surface  of  the  wick  as  well  as  the 
outer  surface.  The  lamp  chimney  not  only  protected 
the  flame  from  drafts  but  also  improved  combustion  by 
increasing  the  supply  of  air.  It  rested  upon  a  per¬ 
forated  flange  below  the  burner.  If  the  glass  chimney 
of  a  modern  kerosene  lamp  be  lifted,  it  will  be  noted 
that  the  flame  flickers  and  smokes  and  that  it  becomes 
steady  and  smokeless  when  the  chimney  is  replaced. 
The  advantages  of  such  a  chimney  are  obvious  now, 
but  Argand  for  his  achievements  is  entitled  to  a  place 
among  the  great  men  who  have  borne  the  torch  of 
civilization.  He  took  the  first  step  toward  adequate 
artificial  light  and  opened  a  new  era  in  lighting. 

The  various  improvements  of  the  oil-lamp  achieved 
by  Argand  combined  to  effect  complete  combustion, 
with  the  result  that  a  steady,  smokeless  lamp  of  con¬ 
siderable  luminous  intensity  was  for  the  first  time  avail¬ 
able.  Many  developments  followed,  among  which  was 
a  combination  of  reservoir  and  gravity  feed  which 
maintained  the  oil  at  a  constant  level.  In  later  lamps, 
upon  the  adoption  of  mineral  oil,  this  was  found  un¬ 
necessary,  perhaps  owing  to  the  construction  of  the 
wick  and  to  the  physical  characteristics  of  the  oil  which 
favored  capillary  action  in  the  wick.  However,  the 
height  of  the  oil  in  the  reservoir  of  modern  oil-lamps 
makes  some  difference  in  the  amount  of  light  emitted. 

The  Carcel  lamp,  which  appeared  in  1800,  consisted 


OIL-LAMPS 


55 


of  a  double  piston  operated  by  clockwork.  This  forced 
the  oil  through  a  tube  to  the  burner.  Franchot  in¬ 
vented  the  moderator  lamp  in  1836,  which,  because  of 
its  simplicity  and  efficiency  soon  superseded  many  other 
lamps  designed  for  burning  animal  and  vegetable  oils. 
The  chief  feature  of  the  moderator  lamp  is  a  spiral 
spring  which  forces  the  oil  upward  through  a  vertical 
tube  to  the  burner.  These  are  still  used  to  some  ex¬ 
tent  in  France,  but  owing  to  the  fact  that  “mechani¬ 
cal”  lamps  eventually  were  very  generally  replaced  by 
more  simple  ones,  it  does  not  appear  necessary  to  de¬ 
scribe  these  complex  mechanisms  in  detail. 

When  coal  is  distilled  at  moderate  temperatures, 
volatile  liquids  are  obtained.  These  hydrocarbons,  be¬ 
ing  inflammable,  naturally  attracted  attention  when 
first  known,  and  in  1781  their  use  as  fuel  for  lamps 
was  suggested.  However,  it  was  not  until  1820  that 
the  light  oils  obtained  by  distilling  coal-tar,  a  by-prod¬ 
uct  of  the  coal-gas  industry  which  was  then  in  its  early 
stage  of  development,  were  burned  to  some  extent  in 
the  Holliday  lamp.  In  this  lamp  the  oil  is  contained 
in  a  reservoir  from  the  bottom  of  which  a  fine  metal 
tube  carries  the  oil  down  to  a  rose-burner.  The  oil  is  * 
heated  by  the  flame  and  the  vaporized  mineral  oil 
which  escapes  through  small  orifices  is  burned.  This 
type  of  lamp  has  undergone  many  physical  changes, 
but  its  principle  survives  to  the  present  time  in  the 
gasolene  and  kerosene  burners  hanging  on  a  pole  by 
the  side  of  the  street-peddler’s  stand. 

Although  petroleum  products  were  not  used  to  any 
appreciable  extent  for  illuminating-purposes  until  after 
the  middle  of  the  nineteenth  century,  mineral  oil  is 


56 


ARTIFICIAL  LIGHT 


mentioned  by  Herodotus  and  other  early  writers.  In 
1847  petroleum  was  discovered  in  a  coal-mine  in  Eng¬ 
land,  but  the  supply  failed  in  a  short  time.  However, 
the  discoverer,  Janies  Young,  had  found  that  this  oil 
was  valuable  as  a  lubricant  and  upon  the  failure  of  this 
source  he  began  experiments  in  distilling  oil  from  shale 
found  in  coal  deposits.  These  were  destined  to  form 
the  corner-stone  of  the  oil  industry  in  Scotland.  In 
1850  he  began  producing  petroleum  in  this  manner, 
but  it  was  not  seriously  considered  for  illuminating- 
purposes.  However,  in  Germany  about  this  time  lamps 
were  developed  for  burning  the  lighter  distillates  and 
these  were  introduced  into  several  countries.  But  the 
price  of  these  lighter  oils  was  so  great  that  little  prog¬ 
ress  was  made  until,  in  1859,  Col.  E.  L.  Drake  dis¬ 
covered  oil  in  Pennsylvania.  By  studying  the  geologi¬ 
cal  formations  and  concluding  that  oil  should  be  ob¬ 
tained  by  boring,  Drake  gave  to  the  world  a  means  of 
obtaining  petroleum,  and  in  quantities  which  were  des¬ 
tined  to  reduce  the  price  of  mineral  oil  to  a  level  un¬ 
dreamed  of  theretofore.  To  his  imagination,  which 
saw  vast  reservoirs  of  oil  in  the  depths  of  the  earth, 
the  world  owes  a  great  debt.  Lamps  were  imported 
from  Germany  to  all  parts  of  the  civilized  world  and 
the  kerosene  lamp  became  the  prevailing  light-source. 
Hundreds  of  American  patents  were  allowed  for  oil- 
lamps  and  their  improvements  in  the  next  decade. 

The  crude  petroleum,  of  course,  is  not  fit  for  illum¬ 
inating  purposes,  but  it  contains  components  which  are 
satisfactory.  The  various  components  are  sorted  out 
by  fractional  distillation  and  the  oil  for  burning  in 
lamps  is  selected  according  to  its  volatility,  viscosity, 


LAMPS  OF  A  CENTURY  OR  TWO  AGO 


ELABORATE  FIXTURES  OF  THE  AGE  OF  CANDLES 


OIL-LAMPS 


57 


stability,  etc.  It  must  not  be  so  volatile  as  to  have  a 
dangerously  low  flashing-point,  nor  so  stable  as  to  hin¬ 
der  its  burning  well.  In  this  fractional  distillation  a 
vast  variety  of  products  are  now  obtained.  Gasolene 
is  among  the  lighter  products,  with  a  density  of  about 
0.65 ;  kerosene  has  a  density  of  about  0.80 ;  the  lubricat- 
ing-oils  from  0.85  to  0.95;  and  there  are  many  solids 
such  as  vaseline  and  paraffin  which  are  widely  used  for 
many  purposes.  This  process  of  refining  oils  is  now 
the  source  of  paraffin  for  making  candles,  in  which  it 
is  usually  mixed  with  substances  like  stearin  in  order 
to  raise  its  melting-point. 

Crude  petroleum  possesses  a  very  repugnant  odor; 
it  varies  in  color  from  yellow  to  black;  and  its  specific 
gravity  ranges  from  about  0.80  to  1.00,  but  commonly  is 
between  0.80  and  0.90.  Its  chemical  constitution  is 
chiefly  of  carbon  and  hydrogen,  in  the  approximate 
ratio  of  about  six  to  one  respectively.  It  is  a  mixture 
of  paraffin  hydrocarbons  having  the  general  formula  of 
CnH0n  +  2  and  the  individual  members  of  this  series 
vary  from  CH4  (methane)  to  C15H32  (pentadecane), 
although  the  solid  hydrocarbons  are  still  more  com¬ 
plex.  Petroleum  is  found  in  many  countries  and  the 
United  States  is  particularly  blessed  with  great  stores 
of  it. 

The  ordinary  lamp  consisting  of  a  wick  which  draws 
up  the  mineral  oil  and  feeds  it  to  a  flame  is  efficient 
and  fairly  free  from  danger.  It  requires  care  and  may 
cause  disaster  if  it  is  upset,  but  it  has  been  blamed  un¬ 
justly  in  many  accidents.  A  disadvantage  of  the  kero¬ 
sene  lamp  over  electric  lighting,  for  example,  is  the 
relatively  greater  possibility  of  accidents  through  the 


58 


ARTIFICIAL  LIGHT 


carelessness  of  the  user.  This  point  is  brought  out  in 
statistics  of  fire-insurance  companies,  which  show  that 
the  fires  caused  by  kerosene  lamps  are  much  more 
numerous  than  those  from  other  methods  of  lighting. 
If  in  a  modern  lamp  of  proper  construction  a  close-fit¬ 
ting  wick  is  used  and  the  lamp  is  extinguished  by  turn¬ 
ing  down  and  blowing  across  the  chimney,  there  is  lit¬ 
tle  danger  in  its  use  excepting  accidental  breakage  or 
overturning. 

In  oil-lamps  at  the  present  time  mineral  oils  are 
used  which  possess  flashing-points  above  75°F.  The 
highly  volatile  components  of  petroleum  are  danger¬ 
ous  because  they  form  very  explosive  mixtures  with 
air  at  ordinary  temperatures.  A  mineral  oil  like  kero¬ 
sene,  to  be  used  with  safety  in  lamps,  should  not  be  too 
volatile.  It  is  preferable  that  an  inflammable  vapor 
should  not  be  given  off  at  temperatures  under  120 °F. 
The  oil  must  be  of  such  physical  characteristics  as  to 
be  drawn  up  to  the  burner  by  capillarity  from  the  res¬ 
ervoir  which  is  situated  below.  It  is  volatilized  by  the 
heat  of  the  flame  into  a  mixture  of  hydrogen  and  hydro¬ 
carbon  gases  and  these  are  consumed  under  the  heat 
of  the  process  of  consumption  by  the  oxygen  in  the 
air.  The  resulting  products  of  this  combustion,  if  it 
is  complete,  are  carbon  dioxide  and  water-vapor.  For 
each  candle-power  of  light  per  hour  about  0.24  cubic 
foot  of  carbon  dioxide  and  0.18  cubic  foot  of  water- 
vapor  are  formed  by  a  modern  oil-lamp.  That  an  open 
flame  devours  something  from  the  air  is  easily  demon¬ 
strated  by  enclosing  it  in  an  air-tight  space.  The  flame 
gradually  becomes  feeble  and  smoky  and  finally  goes 
out.  It  will  be  noted  that  a  burning  lamp  will  vitiate 


OIL-LAMPS 


59 


the  atmosphere  of  a  closed  room  by  consuming  the 
oxygen  and  returning  in  its  place  carbon  dioxide.  This 
is  similar  to  the  vitiation  of  the  atmosphere  by  breath¬ 
ing  persons  and  tests  indicate  that  for  each  two  candle- 
power  emitted  by  a  kerosene  flame  the  vitiation  is  equal 
to  that  produced  by  one  adult  person.  Inasmuch  as 
oil-lamps  are  ordinarily  of  10  to  20  candle-power,  it  is 
seen  that  one  lamp  will  consume  as  much  oxygen  as 
several  persons. 

In  order  that  oil-lamps  may  produce  a  brilliant  light 
free  from  smoke,  combustion  must  be  complete.  The 
correct  quantity  of  oil  must  be  fed  to  the  burner  and 
it  must  be  properly  vaporized  by  heat.  If  insufficient 
oil  is  fed,  the  intensity  of  the  light  is  diminished  and 
if  too  much  is  available  at  the  burner,  smoke  and  other 
products  of  incomplete  combustion  will  be  emitted. 
The  wick  is  an  important  factor,  for,  through  capil¬ 
larity,  it  feeds  oil  forcefully  to  the  burner  against  the 
action  of  gravity.  This  action  of  a  wick  is  commonly 
looked  upon  with  indifference  but  in  reality  it  is  caused 
by  an  interesting  and  really  wonderful  phenomenon. 
Wicks  are  usually  made  of  high-grade  cotton  fiber 
loosely  spun  into  coarse  threads  and  these  are  woven 
into  a  loose  plait.  The  wick  must  be  dry  before  being 
inserted  into  the  burner;  and  it  is  desirable  that  it  be 
considerably  longer  than  is  necessary  merely  to  reach 
the  bottom  of  the  reservoir.  A  flame  burning  in  the 
open  will  smoke  because  insufficient  oxygen  is  brought 
in  contact  with  it.  The  injurious  products  of  this  in¬ 
complete  combustion  are  carbon  monoxide  and  oil  va¬ 
pors,  which  are  a  menace  to  health. 

To  supply  the  necessary  amount  of  oxygen  (air)  to 


60 


ARTIFICIAL  LIGHT 


the  flame,  a  forced  draft  is  produced.  Chimneys  are 
simple  means  of  accomplishing  this,  and  this  is  their 
function  whether  on  oil-lamps  or  factories.  Other 
means  of  forced  draft  have  been  used,  such  as  small 
fans  or  compressed  air.  In  the  railway  locomotive  the 
short  smoke-stack  is  insufficient  for  supplying  large 
quantities  of  air  to  the  fire-box  so  the  exhausted  steam 
is  allowed  to  escape  into  the  stack.  With  each  noisy 
puff  of  smoke  a  quantity  of  air  is  forcibly  drawn  into 
the  fire-box  through  the  burning  fuel.  In  the  modern 
oil-lamp  the  rush  of  air  due  to  the  “pull”  of  the  chim¬ 
ney  is  broken  and  the  air  is  diffused  by  the  wire  gauze 
or  holes  at  the  base  of  the  burner.  These  metal  parts, 
being  hot,  also  serve  to  warm  the  oil  before  it  reaches 
the  burning  end  of  the  wick,  thus  serving  to  aid  vapor¬ 
ization  and  combustion. 

The  consumption  of  oil  per  candle-power  per  hour 
varies  considerably  with  the  kind  of  lamp  and  with  the 
character  of  the  oil.  The  average  consumption  of  oil- 
lamps  burning  a  mineral  oil  of  about  0.80  specific  grav¬ 
ity  and  a  rather  high  flashing-point  is  about  50  to  60 
grams  of  oil  per  candle-power  per  hour  for  well- 
designed  flame-lamps.  Kerosene  weighs  about  6.6 
pounds  per  gallon;  therefore,  about  800  candle-power 
hours  per  gallon  are  obtained  from  modern  lamps  em¬ 
ploying  wicks.  Kerosene  lamps  are  usually  of  10  to 
20  candle-power,  although  they  are  made  up  to  100 
candle-power.  These  luminous  intensities  refer  to  the 
maximum  horizontal  candle-power.  The  best  practice 
now  deals  with  the  total  light  output,  which  is  expressed 
in  lumens,  and  on  this  basis  a  consumption  of  one  gal¬ 
lon  of  kerosene  per  hour  would  yield  about  8000  lumens. 


OIL-LAMPS 


61 


Oil-lamps  have  been  devised  in  which  the  oil  is  burned 
as  a  spray  ejected  by  air-pressure.  These  burn  with  a 
large  flame ;  however,  a  serious  feature  is  the  escape  of 
considerable  oil  which  is  not  burned.  These  lamps  are 
used  in  industrial  lighting,  especially  outdoors,  and 
possess  the  advantage  of  consuming  low-grade  oils. 
They  produce  about  700  to  800  candle-power  hours  per 
gallon  of  oil.  Lamps  of  this  type  of  the  larger  sizes 
burn  with  vertical  flames  two  or  three  feet  high.  The 
oil  is  heated  as  it  approaches  the  nozzle  and  is  fairly 
well  vaporized  on  emerging  into  the  air.  The  names  of 
Lucigen,  Wells,  Doty,  and  others  are  associated  with 
this  type  of  lamp  or  torch,  which  is  a  step  in  the  direc¬ 
tion  of  air-gas  lighting. 

During  the  latter  part  of  the  nineteenth  century 
numerous  developments  were  made  which  paralleled 
the  progress  in  gas-ligliting.  Experiments  were  con¬ 
ducted  which  bordered  closely  upon  the  next  epochal 
event  in  light-production — the  appearance  of  the  gas 
mantle.  One  of  these  was  the  use  of  platinum  gauze 
by  Kitson.  He  produced  an  apparatus  similar  to  the 
oil-spray  lamp,  on  a  small  and  more  delicate  scale. 
The  hot  blue  flame  was  not  very  luminous  and  he  at¬ 
tempted  to  obtain  light  by  heating  a  mantle  of  fine 
platinum  gauze.  Although  these  mantles  emitted  a 
brilliant  light  for  a  few  hours,  their  light-emissivity 
was  destroyed  by  carbonization.  After  the  appear¬ 
ance  of  the  Welsbach  mantle,  Kitson ’s  lamp  and  others 
met  with  success  by  utilizing  it.  From  this  point,  at¬ 
tention  was  centered  upon  the  new  wonder,  which  is 
discussed  in  a  later  chapter  after  certain  scientific 
principles  in  light-production  have  been  discussed. 


62 


ARTIFICIAL  LIGHT 


The  kerosene  or  mineral-oil  lamp  was  a  boon  to  light¬ 
ing  in  the  nineteenth  century  and  even  to-day  it  is  a 
blessing  in  many  homes,  especially  in  villages,  in  the 
country,  and  in  the  remote  districts  of  civilization.  Its 
extensive  use  at  the  present  time  is  shown  by  the  fact 
that  about  eight  million  lamp-chimneys  are  now  being 
manufactured  yearly  in  this  country.  It  is  convenient 
and  safe  when  carelessness  is  avoided,  and  is  fairly  free 
from  odor.  Its  vitiation  of  the  atmosphere  may  be 
counteracted  by  proper  ventilation  and  there  remains 
only  the  disadvantage  of  keeping  it  in  order  and  of 
accidental  breakage  and  overturning.  The  kerosene 
lantern  is  widely  used  to-day,  but  the  danger  due  to  ac¬ 
cident  is  ever-present.  The  consequences  of  such  acci¬ 
dents  are  often  serious  and  are  exemplified  in  the  ter¬ 
rible  conflagration  in  Chicago  in  1871,  when  Mrs. 
O’Leary’s  cow  kicked  over  a  lantern  and  started  a  fire 
which  burned  the  city.  Modern  developments  in  light¬ 
ing  are  gradually  encroaching  upon  the  territory  in 
which  the  oil-lamp  has  reigned  supreme  for  many 
years.  Acetylene  plants  were  introduced  to  a  consider¬ 
able  extent  some  time  ago  and  to-day  the  self-contained 
home-lighting  electric  plant  is  being  installed  in  large 
numbers  in  the  country  homes  of  the  land. 


VI 


EARLY  GAS-LIGHTING 

Owing  to  the  fact  that  the  smoky,  flickering  oil-lamp 
persisted  throughout  the  centuries  and  until  the  magic 
touch  of  Argand  in  the  latter  part  of  the  eighteenth 
century  transformed  it  into  a  commendable  light- 
source,  the  reader  is  prepared  to  suppose  that  gas¬ 
lighting  is  of  recent  origin.  Apparently  William  Mur¬ 
dock  in  England  was  the  first  to  install  pipes  for  the 
conveyance  of  gas  for  lighting  purposes.  In  an  article 
in  the  ‘ ‘  Philosophical  Transactions  of  the  Royal 
Society  of  London”  dated  February  25,  1808,  in  which 
he  gives  an  account  of  the  first  industrial  gas-lighting, 
he  states: 

It  is  now  nearly  sixteen  years,  since,  in  a  course  of 
experiments  I  was  making  at  Redruth  in  Cornwall, 
upon  the  quantities  and  qualities  of  the  gases  produced 
by  distillation  from  different  mineral  and  vegetable 
substances,  I  was  induced  by  some  observations  I  had 
previously  made  upon  the  burning  of  coal,  to  try  the 
combustible  property  of  the  gases  produced  from 
xt*  .  .  . 

Inasmuch  as  he  is  credited  with  having  lighted  his 
home  by  means  of  piped  gas,  this  experimental  installa¬ 
tion  may  be  considered  to  have  been  made  in  1792.  In 
his  first  trial  he  burned  the  gas  at  the  open  ends  of  the 
pipes ;  but  finding  this  wasteful,  he  closed  the  ends  and 

G3 


64 


ARTIFICIAL  LIGHT 


in  each  bored  three  small  holes  from  which  the  gas- 
flames  diverged.  It  is  said  that  he  once  used  his  wife’s 
thimble  in  an  emergency  to  close  the  end  of  the  pipe; 
and,  the  thimble  being  much  worn  and  consequently 
containing  a  number  of  small  holes,  tiny  gas-jets 
emerged  from  the  holes.  This  incident  is  said  to  have 
led  to  the  use  of  small  holes  in  his  burners.  He  also 
lighted  a  street  lamp  and  had  bladders  filled  with  gas 
‘  ‘  to  carry  at  night,  with  which,  and  his  little  steam  car¬ 
riage  running  on  the  road,  he  used  to  astonish  the 
people.”  Apparently  unknown  to  Murdock,  previous 

observations  had  been  made  as.  to  the  inflammabilitv  of 

«/ 

gas  from  coal.  Long  before  this  Hr.  Clayton  described 
some  observations  on  coal-gas,  which  he  called  “the 
spirit  of  coals.”  He  filled  bladders  with  this  gas  and 
kept  them  for  some  time.  Upon  his  pricking  one  of 
them  with  a  pin  and  applying  a  candle,  the  gas  burned 
at  the  hole.  Thus  Clayton  had  a  portable  gas-light. 
He  was  led  to  experiment  with  distillation  of  coal  from 
some  experiences  with  gas  from  a  natural  coal  bed, 
and  he  thus  describes  his  initial  laboratory  experiment : 

I  got  some  coal,  and  distilled  it  in  a  retort  in  an  open 
fire.  At  first  there  came  over  only  phlegm,  afterwards 
a  black  oil,  and  then  likewise,  a  spirit  arose  which  I 
could  no  ways  condense ;  but  it  forced  my  lute  and  broke 
my  glasses.  Once  when  it  had  forced  my  lute,  coming 
close  thereto,  in  order  to  try  to  repair  it,  I  observed 
that  the  spirit  which  issued  out  caught  fire  at  the  flame 
of  the  candle,  and  continued  burning  with  violence  as  it 
issued  out  in  a  stream,  which  I  blew  out,  and  lighted 
again  alternately  several  times. 

He  then  turned  his  attention  to  saving  some  of  the 


EARLY  GAS-LIGHTING 


65 


gas  and  hit  upon  the  use  of  bladders.  He  was  sur¬ 
prised  at  the  amount  of  gas  which  was  obtained  from 
a  small  amount  of  coal;  for,  as  he  stated,  “the  spirit 
continued  to  rise  for  several  hours,  and  tilled  the  blad¬ 
ders  almost  as  fast  as  a  man  could  have  blown  them 
with  his  mouth ;  and  yet  the  quantity  of  coals  distilled 
was  inconsiderable.  ” 

Although  this  account  appeared  in  the  Transactions 
of  the  Royal  Society  in  1739,  there  is  strong  evidence 
that  Dr.  Clayton  had  written  it  many  years  before,  at 
least  prior  to  1691. 

But  before  entering  further  into  the  early  history 
of  gas-lighting,  it  is  interesting  to  inquire  into  the 
knowledge  possessed  in  the  seventeenth  century  per¬ 
taining  to  natural  and  artificial  gas.  Doubtless  there 
are  isolated  instances  throughout  history  of  encounters 
with  natural  gas.  Surely  observant  persons  of  bygone 
ages  have  noted  a  small  flame  emanating  from  the  end 
of  a  stick  whose  other  end  was  burning  in  a  bonfire  or 
in  the  fireplace.  This  is  a  gas-plant  on  a  small  scale ; 
for  the  gas  is  formed  at  the  burning  end  of  the  wooden 
stick  and  is  conducted  through  its  hollow  center  to  the 
cold  end,  where  it  will  burn  if  lighted.  If  a  piece  of 
paper  be  rolled  into  the  form  of  a  tube  and  inclined 
somewhat  from  a  horizontal  position,  inflammable  gas 
will  emanate  from  the  upper  end  if  the  lower  end  is 
burning.  By  applying  a  match  near  the  upper  end, 
we  can  ignite  this  jet  of  gas.  However,  it  is  certain 
that  little  was  known  of  gas  for  illuminating  purposes 
before  the  eighteenth  century. 

The  literature  of  an  ancient  nation  is  often  referred 
to  as  revealing  the  civilization  of  the  period.  Surely 


66 


ARTIFICIAL  LIGHT 


the  scientific  literature  which  deals  with  concrete  facts 
is  an  exact  indicator  of  the  technical  knowledge  of  a 
period!  That  little  was  known  of  natural  gas  and 
doubtless  of  artificial  gas  in  the  seventeenth  century  is 
shown  by  a  brief  report  entitled  “A  Well  and  Earth 
in  Lancashire  taking  Fire  at  a  Candle,  ”  by  Tho.  Shirley 
in  the  Transactions  of  the  Royal  Society  in  1667. 
Much  of  the  quaint  charm  of  the  original  is  lost  by 
inability  to  present  the  text  in  its  original  form,  but 
it  is  reproduced  as  closely  as  practicable.  The  report 
was  as  follows : 

About  the  latter  End  of  Feb .  1659,  returning  from  a 
Journey  to  my  House  in  Wigan,  I  was  entertained  with 
the  Relation  of  an  odd  Spring  situated  in  one  Mr. 
Hawkley’s  Ground  (if  I  mistake  not)  about  a  Mile 
from  the  Town,  in  that  Road  which  leads  to  Warring¬ 
ton  and  Chester:  The  People  of  this  Town  did  confi¬ 
dently  affirm,  That  the  Water  of  this  Spring  did  burn 
like  Oil. 

When  we  came  to  the  said  Spring  (being  5  or  6  in 
Company  together)  and  applied  a  lighted  Candle  to  the 
Surface  of  the  Water;  there  was  ’tis  true,  a  large 
Flame  suddenly  produced,  which  burnt  the  Foot  of  a 
Tree,  growing  on  the  Top  of  a  neighbouring  Bank,  the 
Water  of  which  Spring  filled  a  Hitch  that  was  there, 
and  covered  the  Burning-place;  I  applied  the  lighted 
Candle  to  divers  Parts  of  the  Water  contained  in  the 
said  Hitch,  and  found,  as  I  expected,  that  upon  the 
Touch  of  the  Candle  and  the  Water  the  Flame  was 
extinct. 

Again,  having  taken  up  a  Hish  full  of  water  at  the 
flaming  Place,  and  held  the  lighted  Candle  to  it,  it  went 
out.  Yet  I  observed  that  the  Water,  at  the  Burning- 
place,  did  boil,  and  heave,  like  Water  in  a  Pot  upon  the 


EARLY  GAS-LIGHTING 


67 


Fire,  tho  ’  by  putting  my  Hand  into  it,  I  could  not  per¬ 
ceive  it  so  much  as  warm. 

This  Boiling  I  conceived  to  proceed  from  the  Erup¬ 
tion  of  some  bituminous  or  sulphureous  Fumes;  con¬ 
sidering  this  Place  was  not  above  30  or  40  Yards  dis¬ 
tant  from  the  Mouth  of  a  Coal-Pit  there:  And  indeed 
Wigan ,  Ashton,  and  the  whole  Country,  for  many  Miles 
compass,  is  underlaid  with  Coal.  Then,  applying  my 
Hand  to  the  Surface  of  the  Burning-place  of  the  Water, 
I  found  a  strong  Breath,  as  it  were  a  Wind,  to  bear 
against  my  Hand. 

When  the  Water  was  drained  away,  I  applied  the 
Candle  to  the  Surface  of  the  dry  Earth,  at  the  same 
Point  where  the  Water  burned  before;  the  Fumes  took 
fire,  and  burned  very  bright  and  vigorous.  The  Cone 
of  the  Flame  ascended  a  Foot  and  a  half  from  the 
Superficies  of  the  Earth;  and  the  Basis  of  it  was  of  the 
Compass  of  a  Man’s  Hat  about  the  Brims.  I  then 
caused  a  Bucket  full  of  Water  to  be  pour’d  on  the 
Fire,  by  which  it  was  presently  quenched.  I  did  not 
perceive  the  Flame  to  be  discoloured  like  that  of  sul¬ 
phurous  Bodies,  nor  to  have  any  manifest  Scent  with  it. 
The  Fumes,  when  they  broke  out  of  the  Earth,  and 
press  yd  against  my  Hand,  were  not,  to  my  best  Remem¬ 
brance,  at  all  hot. 

Turning  again  to  Dr.  Clayton’s  experiments,  we  see 
that  he  pointed  out  striking  and  valuable  properties  of 
coal-gas  but  apparently  gave  no  attention  to  its  useful 
purposes.  Furthermore,  his  account  appears  to  have 
attracted  no  particular  notice  at  the  time  of  its  publi¬ 
cation  in  1739.  Dr.  Richard  Watson  in  1767  described 
the  results  of  experiments  which  he  had  been  making 
with  the  products  arising  from  the  distillation  of  coal. 
In  his  process  he  permitted  the  gas  to  ascend  through 


68 


ARTIFICIAL  LIGHT 


curved  tubes,  and  he  particularly  noted  “its  great  in¬ 
flammability  as  well  as  elasticity/ ’  He  also  observed 
that  “it  retained  the  former  property  after  it  had 
passed  through  a  great  quantity  of  water.”  His  pub¬ 
lished  account  dealt  with  a  variety  of  facts  and  compu¬ 
tations  pertaining  to  the  quantities  of  coke,  tar,  etc., 
produced  from  different  kinds  of  coal  and  was  a  scien¬ 
tific  work  of  value,  but  apparently  the  usefulness  of 
the  property  of  inflammability  of  coal-gas  did  not  occur 
to  him. 

It  is  usually  the  habit  of  the  scientific  explorer  of 
nature  to  return  from  excursions  into  her  unfrequented 
recesses  with  new  knowledge,  to  place  it  upon  exhibi¬ 
tion,  and  to  return  for  more.  The  inventor  passes  by 
and  sees  applications  for  some  of  these  scientific 
trophies  which  are  productive  of  momentous  conse¬ 
quences  to  mankind.  Sir  Humphrey  Davy  described 
his  primitive  arc-lamp  three  quarters  of  a  century  be¬ 
fore  Brush  developed  an  arc-lamp  for  practical  pur¬ 
poses.  Maxwell  and  Hertz  respectively  predicted  and 
produced  electromagnetic  waves  long  before  Marconi 
applied  this  knowledge  and  developed  “wireless” 
telegraphy.  In  a  similar  manner  scientific  accounts  of 
the  production  and  properties  of  coal-gas  antedated  by 
many  years  the  initial  applications  made  by  Murdock 
to  illuminating  purposes. 

Up  to  the  beginning  of  the  nineteenth  century  the 
civilized  world  had  only  a  faint  glimpse  of  the  illumi¬ 
nating  property  of  gas,  but  practicable  gas-lighting 
was  destined  soon  to  be  an  epochal  event  in  the  prog¬ 
ress  of  lighting.  The  dawn  of  modern  science  was 
coincident  with  the  dawn  of  a  luminous  era. 


EARLY  GAS-LIGHTING 


69 


At  Soho  foundry  in  1798  Murdock  constructed  an 
apparatus  which  enabled  him  to  exhibit  his  lighting- 
plan  on  a  larger  scale  and  to  experiment  on  purifying 
and  burning  the  gas  so  as  to  eliminate  odor  and  smoke. 
Soho  was  an  unique  institution  described  as  a  place 

to  which  men  of  genius  wTere  invited  and  resorted  from 
every  civilized  country,  to  exercise  and  to  display  their 
talents.  The  perfection  of  the  manufacturing  arts  was 
the  great  and  constant  aim  of  its  liberal  and  enlight¬ 
ened  proprietors,  Messrs.  Boulton  and  Watt;  and  who¬ 
ever  resided  there  was  surrounded  by  a  circle  of  scien¬ 
tific,  ingenious,  and  skilful  men,  at  all  times  ready  to 
carry  into  effect  the  inventions  of  each  other. 

The  Treaty  of  Amiens,  which  gave  to  England  the 
peace  she  was  sorely  in  need  of,  afforded  Murdock  an 
opportunity  in  1802  favorable  for  making  a  public  dis¬ 
play  of  gas-lighting.  The  illumination  of  the  Soho 
works  on  this  occasion  is  described  as  “one  of  extraor¬ 
dinary  splendour.  ”  The  fronts  of  the  extensive  range 
of  buildings  were  ornamented  with  a  large  number  of 
devices  which  displayed  the  variety  of  forms  of  gas¬ 
lights.  At  that  time  this  was  a  luminous  spectacle  of 
great  novelty  and  the  populace  came  from  far  and 
wide  “to  gaze  at,  and  to  admire,  this  wonderful  display 
of  the  combined  effects  of  science  and  art.  ” 

Naturally,  Murdock  had  many  difficulties  to  over¬ 
come  in  these  early  days,  but  he  possessed  skill  and 
perseverance.  His  first  retorts  for  distilling  coal  were 
similar  to  the  common  glass  retort  of  the  chemist. 
Next  he  tried  cast-iron  cylinders  placed  perpendicu¬ 
larly  in  a  common  furnace,  and  in  each  were  put  about 
fifteen  pounds  of  coal.  In  1804  he  constructed  them 


70 


ARTIFICIAL  LIGHT 


with  doors  at  each  end,  for  feeding  coal  and  extracting 
coke  respectively,  but  these  were  found  inconvenient. 
In  his  first  lighting  installation  in  the  factory  of 
Phillips  and  Lee  in  1805  he  used  a  large  retort  of  the 
form  of  a  bucket  with  a  cover  on  it.  Inside  he  installed 
a  loose  cage  of  grating  to  hold  the  coal.  When  car¬ 
bonization  was  complete  the  coke  could  be  removed  as 
a  whole  by  extracting  this  cage.  This  retort  had  a  ca¬ 
pacity  of  fifteen  hundred  pounds  of  coal.  He  labored 
with  mechanical  details,  varied  the  size  and  shape  of 
the  retorts,  and  experimented  with  different  tempera¬ 
tures,  with  the  result  that  he  laid  a  solid  foundation 
for  coal-gas  lighting.  For  his  achievements  he  is  en¬ 
titled  to  an  honorable  place  among  the  torch-bearers 
of  civilization. 

The  epochal  feature  of  the  development  of  gas-light¬ 
ing  is  that  here  was  a  possibility  for  the  first  time  of 
providing  lighting  as  a  public  utility.  In  the  early 
years  of  the  nineteenth  century  the  foundation  was  laid 
for  the  great  public-utility  organizations  of  the  present 
time.  Furthermore,  gas-lighting  was  an  improvement 
over  candles  and  oil-lamps  from  the  standpoints  of  con¬ 
venience,  safety,  and  cost.  The  latter  points  are 
emphasized  by  Murdock  in  his  paper  presented  before 
the  Royal  Society  in  1808,  in  which  he  describes  the 
first  industrial  installation  of  gas-lighting.  He  used 
two  types  of  burners,  the  Argand  and  the  cockspur. 
The  former  resembled  the  Argand  lamp  in  some  re¬ 
spects  and  the  latter  was  a  three-flame  burner  suggest¬ 
ing  a  fleur-de-lis.  In  this  installation  there  were  271 
Argand  burners  and  636  cockspurs.  Each  of  the  for¬ 
mer  ‘ 4 gave  a  light  equal  to  that  of  four  candles;  and 


EARLY  GAS-LIGHTING 


71 


each  of  the  latter,  a  light  equal  to  two  and  a  quarter  of 
the  same  candles;  making  therefore  the  total  of  the 
gas  light  a  little  more  than  2500  candles.  ’ *  The  candle 
to  which  he  refers  was  a  mold  candle  “of  six  in  the 
pound  ”  and  its  light  was  considered  a  standard  of 
luminous  intensity  when  it  was  consuming  tallow  at  the 
rate  of  0.4  oz.  (175  grains)  per  hour.  Thus  the  candle 
became  very  early  a  standard  light-source  and  has 
persisted  as  such  (with  certain  variations  in  the  speci¬ 
fications)  until  the  present  time.  However,  during 
recent  years  other  standard  light-sources  have  been 
devised. 

According  to  Murdock,  the  yearly  cost  of  gas-lighting 
in  this  initial  case  was  600  pounds  sterling  after  allow¬ 
ing  generously  for  interest  on  capital  invested  and  de¬ 
preciation  of  the  apparatus.  The  cost  of  furnishing 
the  same  amount  of  light  by  means  of  candles  he  com¬ 
puted  to  be  2000  pounds  sterling.  This  comparison 
was  on  the  basis  of  an  average  of  two  hours  of  artifi¬ 
cial  lighting  per  day.  On  the  basis  of  three  hours  of 
artificial  lighting  per  day,  the  relative  cost  of  gas-  and 
candle-lighting  was  about  one  to  five.  Murdock  was 
characteristically  modest  in  discussing  his  achieve¬ 
ments  and  his  following  statement  should  be  read  with 
the  conditions  of  the  year  1808  in  mind: 

The  peculiar  softness  and  clearness  of  this  light  with 
its  almost  unvarying  intensity,  have  brought  it  into 
great  favour  with  the  work  people.  And  its  being  free 
from  the  inconvenience  and  danger,  resulting  from 
sparks  and  frequent  snuffing  of  candles,  is  a  circum¬ 
stance  of  material  importance,  as  tending  to  diminish 
the  hazard  of  fire,  to  which  cotton  mills  are  known  to 
be  exposed. 


72 


ARTIFICIAL  LIGHT 


Although  this  installation  in  the  mill  of  Phillips  and 
Lee  is  the  first  one  described  by  Murdock,  in  reality  it 
is  not  the  first  industrial  gas-lighting  installation. 
During  the  development  of  gas  apparatus  at  the  Soho 
works  and  after  his  luminous  display  in  1802,  he  gradu¬ 
ally  extended  gas-ligliting  to  all  the  principal  shops. 
However,  this  in  a  sense  was  experimental  work. 
Others  were  applying  their  knowledge  and  ingenuity 
to  the  problem  of  making  gas-lighting  practicable,  but 
Murdock  has  been  aptly  termed  “the  father  of  gas¬ 
lighting.  ’  9  Among  the  pioneers  was  Le  Bon  in  France, 
Becher  in  Munich,  and  Winzler  or  Winsor,  a  German 
who  was  attracted  to  the  possibilities  of  gas-lighting 
by  an  exhibition  which  Le  Bon  gave  in  Paris  in  1802. 
Winsor  learned  that  Le  Bon  had  been  granted  a  patent 
in  Paris  in  1799  for  making  an  illuminating  gas  from 
wood  and  tried  to  obtain  the  rights  for  Germany. 
Being  unsuccessful  in  this,  he  set  about  to  learn  the 
secrets  of  Le  Bon’s  process,  which  he  did,  perhaps 
largely  owing  to  an  accumulation  of  information 
directly  from  the  inventor  during  the  negotiations. 
Winsor  then  turned  to  England  as  a  fertile  field  for  the 
exploitation  of  gas-lighting  and  after  conducting  ex¬ 
periments  in  London  for  some  time  he  made  plans  to 
organize  the  National  Heat  and  Light  Co. 

Winsor  was  primarily  a  promoter,  with  little  or  no 
technical  knowledge;  for  in  his  claims  and  advertise¬ 
ments  he  disregarded  facts  with  a  facility  possessed 
only  by  the  ignorant.  He  boasted  of  his  inventions 
and  discoveries  in  the  most  hyperbolical  language, 
which  was  bound  to  provoke  a  controversy.  Neverthe¬ 
less,  he  was  clever  and  in  1803  he  publicly  exhibited  his 


EARLY  GAS-LIGHTING 


73 


plan  of  lighting  by  means  of  coal-gas  at  the  Lyceum 
Theatre  in  London.  He  gave  lectures  accompanied  by 
interesting  and  instructive  experiments  and  in  this 
manner  attracted  the  public  to  his  exhibition.  All  this 
time  he  was  promoting  his  company,  but  his  promoting 
instinct  caused  his  representations  to  be  extravagant 
and  deceptive,  which  exposed  him  to  the  ridicule  and 
suspicion  of  learned  men.  His  attempt  to  obtain  cer¬ 
tain  exclusive  rights  by  Act  of  Parliament  failed  be¬ 
cause  of  opposition  of  scientific  men  toward  his  claims 
and  of  the  stand  which  Murdock  justly  made  in  self¬ 
protection.  These  years  of  controversy  yield  enter¬ 
taining  literature  for  those  who  choose  to  read  it,  but 
unfortunately  space  does  not  permit  dwelling  upon  it. 
The  investigations  by  committees  of  Parliament  also 
afford  amusing  side-lights.  Throughout  all  this  Mur¬ 
dock  appeared  modest  and  conservative  and  had  the 
support  of  reputable  scientific  men,  but  Winsor  main¬ 
tained  extravagant  claims. 

During  one  of  these  investigations  Sir  Humphrey 
Davy  was  examined  by  a  committee  from  the  House  of 
Commons  in  1809.  He  refuted  Winsor ’s  claims  for  a 
superior  coke  as  a  by-product  and  stated  that  the  pro¬ 
duction  of  gas  by  the  distillation  of  coal  had  been  well 
known  for  thirty  or  forty  years  and  the  production  of 
tar  as  long.  He  stated  that  it  was  the  opinion  of  the 
Council  of  the  Royal  Society  that  Murdock  was  the 
first  person  to  apply  coal-gas  to  lighting  in  actual 
practice.  As  secretary  of  the  Society,  Sir  Humphrey 
Davy  stated  that  at  the  last  session  it  had  bestowed 
the  Count  Rumford  medal  upon  Murdock  for  4 ‘his 
economical  application  of  the  gas  light.” 


74 


ARTIFICIAL  LIGHT 


Winsor  proceeded  to  float  his  company  without 
awaiting  the  Act  of  Parliament  and  in  1807  lighted  a 
street  in  Pall  Mall.  Through  the  opposition  which  he 
aroused,  and  owing  to  the  just  claims  of  priority  on  the 
part  of  Murdock,  the  bill  to  incorporate  the  National 
Heat  and  Light  Co.  with  a  capital  of  200,000  pounds 
sterling  was  thrown  out.  However,  he  succeeded  in 
1812  in  receiving  a  charter  very  much  modified  in  form, 
for  the  Chartered  Gas  Light  and  Coke  Co.  which  was 
the  forerunner  of  the  present  London  Gas  Light  and 
Coke  Co. 

The  conditions  imposed  upon  this  company  as  pre¬ 
sented  in  an  early  treatise  on  gas-lighting  (by  Accum 
in  1818)  were  as  follows: 

The  power  and  authorities  granted  to  this  corporate 
body  are  very  restricted  and  moderate.  The  individu¬ 
als  composing  it  have  no  exclusive  privilege;  their 
charter  does  not  prevent  other  persons  from  entering 
into  competition  with  them.  Their  operations  are  con¬ 
fined  to  the  metropolis,  where  they  are  bound  to  furnish 
not  only  a  stronger  and  better  light  to  such  streets  and 
parishes  as  chuse  to  be  lighted  with  gas,  but  also  at  a 
cheaper  price  than  shall  be  paid  for  lighting  the  said 
streets  with  oil  in  the  usual  manner.  The  corporation 
is  not  permitted  to  traffic  in  machinery  for  manufactur¬ 
ing  or  conveying  the  gas  into  private  houses,  their  capi¬ 
tal  or  joint  stock  is  limited  to  £200,000,  and  his  Majesty 
has  the  power  of  declaring  the  gas-light  charter  void 
if  the  company  fail  to  fulfil  the  terms  of  it. 

The  progress  of  this  early  company  was  slow  at  first, 
but  with  the  appointment  of  Samuel  Clegg  as  engineer 
in  1813  an  era  of  technical  developments  began.  New 
stations  were  built  and  many  improvements  were  in- 


EARLY  GAS-LIGHTING 


75 


troduccd.  By  improving  the  methods  of  purifying 
the  gas  a  great  advance  was  made.  The  utility  of  gas¬ 
lighting  grew  apace  as  the  prejudices  disappeared, 
but  for  a  long  time  the  stock  of  the  company  sold  at  a 
price  far  below  par.  About  this  time  the  first  gas  ex¬ 
plosion  took  place  and  the  members  of  the  Royal  Soci¬ 
ety  set  a  precedent  which  has  lived  and  thrived:  they 
appointed  a  committee  to  make  an  inquiry.  But  ap¬ 
parently  the  inquiry  was  of  some  value,  for  it  led  “to 
some  useful  alterations  and  new  modifications  in  its 
apparatus  and  machinery.” 

Many  improvements  were  being  introduced  during 
these  years  and  one  of  them  in  1816  increased  the  gase¬ 
ous  product  from  coal  by  distilling  the  tar  which  was 
obtained  during  the  first  distillation.  In  1816  Clegg 
obtained  a  patent  for  a  horizontal  rotating  retort;  for 
an  apparatus  for  purifying  coal-gas  with  “cream  of 
lime”;  and  for  a  rotative  gas-meter. 

Before  progressing  too  far,  we  must  mention  the 
early  work  of  William  Henry.  In  1804  he  described 
publicly  a  method  of  producing  coal-gas.  Besides 
making  experiments  on  production  and  utilization  of 
coal-gas  for  lighting,  he  devoted  his  knowledge  of 
chemistry  to  the  analysis  of  the  gas.  He  also  made 
analytical  studies  of  the  relative  value  of  wood,  peat, 
oil,  wax,  and  different  kinds  of  coal  for  the  distillation 
of  gas.  His  chemical  analyses  showed  to  a  consider¬ 
able  extent  the  properties  of  carbureted  hydrogen  upon 
which  illuminating  value  depended.  The  results  of  his 
work  were  published  in  various  English  journals  be¬ 
tween  1805  and  1825  and  they  contributed  much  to  the 
advancement  of  gas-lighting. 


76 


ARTIFICIAL  LIGHT 


Although  Clegg’s  original  gas-meter  was  compli¬ 
cated  and  cumbersome,  it  proved  to  be  a  useful  device. 
In  fact,  it  appears  to  have  been  the  most  original  and 
beneficial  invention  occasioned  by  early  gas-lighting. 
Later  Samuel  Crosley  greatly  improved  it,  with  the 
result  that  it  was  introduced  to  a  considerable  extent ; 
but  by  no  means  was  it  universally  adopted.  Another 
improvement  made  by  Clegg  at  this  time  was  a  device 
which  maintained  the  pressure  of  gas  approximately 
constant  regardless  of  the  pressure  in  the  gasometer 
or  tank.  Clegg  retired  from  the  service  of  the  gas 
company  in  1817  after  a  record  of  accomplishments 
which  glorifies  his  name  in  the  annals  of  gas-lighting. 
Murdock  is  undoubtedly  entitled  to  the  distinction  of 
having  been  the  first  person  who  applied  gas-lighting 
to  large  private  establishments,  but  Clegg  overcame 
many  difficulties  and  was  the  first  to  illuminate  a  whole 
town  by  this  means. 

In  London  in  1817  over  300,000  cubic  feet  of  coal-gas 
was  being  manufactured  daily,  an  amount  sufficient  to 
operate  76,500  Argand  burners  yielding  6  candle-power 
each.  Gas-lighting  was  now  exciting  great  interest  and 
was  firmly  established.  Westminster  Bridge  was 
lighted  by  gas  in  1813,  and  the  streets  of  Westminster 
during  the  following  year.  Gas-lighting  became  popu¬ 
lar  in  London  by  1816  and  in  the  course  of  the  next  few 
years  it  was  adopted  by  the  chief  cities  and  towns  in 
the  United  Kingdom  and  on  the  Continent.  It  found 
its  way  into  the  houses  rather  slowly  at  first,  owing  to 
apprehension  of  the  attendant  dangers,  to  the  lack  of 
purification  of  the  gas,  and  to  the  indifferent  service. 


EARLY  GAS-LIGHTING  77 

It  was  not  until  the  latter  half  of  the  nineteenth  cen¬ 
tury  that  it  was  generally  used  in  residences. 

The  gas-burner  first  employed  by  Murdock  received 
the  name  “oockspur”  from  the  shape  of  the  flame. 
This  had  an  illuminating  value  equivalent  to  about  one 
candle  for  each  cubic  foot  of  gas  burned  per  hour. 
The  next  step  was  to  flatten  the  welded  end  of  the  gas- 
pipe  and  to  bore  a  series  of  holes  in  a  line.  From  the 
shape  of  the  flames  this  form  of  burner  received  the 
name  “cockscomb.”  It  was  somewhat  more  efficient 
than  the  cockspur  burner.  The  next  obvious  step  was 
to  slit  the  end  of  the  pipe  by  means  of  a  fine  saw. 
From  this  slit  the  gas  was  burned  as  a  sheet  of  flame 
called  the  “bats-wing.”  In  1820  Nielson  made  a 
burner  which  allowed  two  small  jets  to  collide  and  thus 
form  a  flat  flame.  The  efficiency  of  this  “fish-tail” 
burner  was  somewhat  higher  than  that  of  the  earlier 
ones.  Its  flame  was  steadier  because  it  was  less  in¬ 
fluenced  by  drafts  of  air.  In  1853  Frankland  showed 
an  Argand  burner  consisting  of  a  metal  ring  containing 
a  series  of  holes  from  which  jets  of  gas  issued.  The 
glass  chimney  surrounded  these,  another  chimney,  ex¬ 
tending  somewhat  lower,  surrounded  the  whole,  and  a 
glass  plate  closed  the  bottom.  The  air  to  be  fed  to 
the  gas-jets  came  downward  between  the  two  chimneys 
and  was  heated  before  it  reached  the  burner.  This 
increased  the  efficiency  by  reducing  the  amount  of  cool¬ 
ing  at  the  burner  by  the  air  required  for  combustion. 
This  improvement  was  in  reality  the  forerunner  of  the 
regenerative  lamps  which  were  developed  later. 

In  1854  Bowditch  brought  out  a  regenerative  lamp 


78 


ARTIFICIAL  LIGHT 


and,  owing  to  the  excessive  publicity  which  this  lamp 
obtained,  he  is  generally  credited  with  the  inception  of 
the  regenerative  burner.  This  principle  was  adopted 
in  several  lamps  which  came  into  use  later.  They 
were  all  based  upon  the  principle  of  heating  both  the 
gas  and  the  air  required  for  combustion  prior  to  their 
reaching  the  burner.  The  burner  is  something  like  an 
inverted  Argand  arranged  to  produce  a  circular  flame 
projecting  downward  with  a  central  cusp.  The  air- 
and  gas-passages  are  directly  above  the  flame  and  are 
heated  by  it.  In  1879  Friedrich  Siemens  brought  out  a 
lamp  of  this  type  which  was  adapted  from  a  device 
originally  designed  for  heating  purposes,  owing  to  the 
superior  light  which  was  produced.  This  was  the  best 
gas-lamp  up  to  that  time.  Later,  Wenham,  Cromartie, 
and  others  patented  lamps  operating  on  this  same 
principle. 

Murdock  early  modified  the  Argand  burner  to  meet 
the  requirements  of  burning  gas  and  by  using  the  chim¬ 
ney  obtained  better  combustion  and  a  steadier  flame 
than  from  the  open  burners.  He  and  others  recognized 
that  the  temperature  of  the  flame  had  a  considerable 
effect  upon  the  amount  of  light  emitted  and  non-con¬ 
ducting  material  such  as  steatite  was  substituted  for 
the  metal,  which  cooled  the  flame  by  conducting  heat 
from  it.  These  were  the  early  steps  which  led  finally 
to  the  regenerative  burner. 

The  increasing  efficiency  of  the  various  gas-burners 
is  indicated  by  the  following,  which  are  approximately 
the  candle-power  based  upon  equal  rates  of  consump¬ 
tion,  namely,  one  cubic  foot  of  gas  per  hour: 


EABLY  GAS-LIGHTING 


79 


Candle-power 
per  cubic  foot  of 
gas  per  hour 

Fish-tail  flames,  depending-  upon  size  ....  0.6  to  2.5 
Argand,  depending  upon  improvements  .  .  2.9  to  3.5 
Regenerative  .  7  to  10 

It  is  seen  that  the  possibilities  of  gas  lighting  were 
recognized  in  several  countries,  all  of  which  contributed 
to  its  development.  Some  of  the  earlier  accounts  have 
been  drawn  chiefly  from  England,  but  these  are  in¬ 
tended  merely  to  serve  as  examples  of  the  difficulties 
encountered.  Doubtless,  similar  controversies  arose 
in  other  countries  in  which  pioneers  were  also  nursing 
gas-lighting  to  maturity.  However,  it  is  certain  that 
much  of  the  early  progress  of  lighting  of  this  character 
was  fathered  in  England.  Gas-lighting  was  destined 
to  become  a  thriving  industry,  and  is  of  such  im¬ 
portance  in  lighting  that  another  chapter  is  given  its 
modem  developments. 


THE  SCIENCE  OF  LIGHT-PRODUCTION 


In  previous  chapters  much  of  the  historical  develop¬ 
ment  of  artificial  lighting  has  been  presented  and  sev¬ 
eral  subjects  have  been  traced  to  the  modern  period 
which  marks  the  beginning  of  an  intensive  attack  by 
scientists  upon  the  problems  pertaining  to  the  produc¬ 
tion  of  efficient  and  adequate  light-sources.  Many  his¬ 
torical  events  remain  to  be  touched  upon  in  later  chap¬ 
ters,  but  it  is  necessary  at  this  point  for  the  reader  to 
become  acquainted  with  certain  general  physical  prin¬ 
ciples  in  order  that  he  may  read  with  greater  interest 
some  of  the  chapters  which  follow.  It  is  seen  that  from 
a  standpoint  of  artificial  lighting,  the  “dark  age”  ex¬ 
tended  well  into  the  nineteenth  century.  Oil-lamps  and 
gas-lighting  began  to  be  seriously  developed  at  the 
beginning  of  the  last  century,  but  the  pioneers  gave  at¬ 
tention  chiefly  to  mechanical  details  and  somewhat  to 
the  chemistry  of  the  fuels.  It  was  not  until  the  science 
of  physics  was  applied  to  light-sources  that  rapid  prog¬ 
ress  was  made. 

All  the  light-sources  used  throughout  the  ages,  and 
nearly  all  modern  ones,  radiate  light  by  virtue  of  the 
incandescence  of  solids  or  of  solid  particles  and  it  is  an 
interesting  fact  that  carbon  is  generally  the  solid  which 
emits  light.  This  is  due  to  various  physical  character¬ 
istics  of  carbon,  the  chief  one  being  its  extremely  high 


THE  SCIENCE  OF  LIGHT-PRODUCTION  81 


melting-point.  However,  most  practicable  light- 
sources  of  the  past  and  present  may  be  divided  into 
two  general  classes :  (1)  Those  in  which  solids  or  solid 

particles  are  heated  by  their  own  combustion,  and  (2) 
those  in  which  the  solids  are  heated  by  some  other 
means.  Some  light-sources  include  both  principles  and 
some  perhaps  cannot  be  included  under  either  principle 
without  qualification.  The  luminous  flames  of  burning 
material  such  as  those  of  wood-splinters,  candles,  oil- 
lamps,  and  gas-jets,  and  the  glowing  embers  of  burning 
material  appear  in  the  first  class ;  and  incandescent  gas- 
mantles,  electric  filaments,  and  arc-lamps  to  some  ex¬ 
tent  are  representative  of  the  second  class.  Certain 
‘ ‘flaming’ ’  arcs  involve  both  principles,  but  the  light  of 
the  firefly,  phosphorescence,  and  incandescent  gas  in 
“vacuum”  tubes  cannot  be  included  in  this  simplified 
classification.  The  status  of  these  will  become  clear 
later. 

It  has  been  seen  that  flames  have  been  prominent 
sources  of  artificial  light ;  and  although  of  low  luminous 
efficiency,  they  still  have  much  to  commend  them  from 
the  standpoints  of  portability,  convenience,  and  sub¬ 
division.  The  materials  which  have  been  burned  for 
light,  whether  solid  or  liquid,  are  rich  in  carbon,  and 
the  solid  particles  of  carbon  by  virtue  of  their  incan¬ 
descence  are  responsible  for  the  brightness  of  a  flame. 
A  jet  of  pure  hydrogen  gas  will  burn  very  hot  but  with 
so  low  a  brightness  as  to  be  barely  visible.  If  solid 
particles  are  injected  into  the  flame,  much  more  light 
usually  will  be  emitted.  A  gas-burner  of  the  Bunsen 
type,  in  which  complete  combustion  is  obtained  by  mix¬ 
ing  air  in  proper  proportions  with  the  gas,  gives  a  hot 


82 


ARTIFICIAL  LIGHT 


flame  which  is  of  a  pale  blue  color.  Upon  the  closing 
of  the  orifice  through  which  air  is  admitted,  the  flame 
becomes  bright  and  smoky.  The  flame  is  now  less  hot, 
as  indicated  by  the  presence  of  smoke  or  carbon  parti¬ 
cles,  and  combustion  is  not  complete.  However,  it  is 
brighter  because  the  solid  particles  of  carbon  in  pass¬ 
ing  upward  through  the  flame  become  heated  to  tem¬ 
peratures  at  which  they  glow  and  each  becomes  a  minia¬ 
ture  source  of  light. 

A  close  observer  will  notice  that  the  flame  from  a 
match,  a  candle,  or  a  gas-jet,  is  not  uniformly  bright. 
The  reader  may  verify  this  by  lighting  a  match  and 
observing  the  flame.  There  is  always  a  bluish  or 
darker  portion  near  the  bottom.  In  this  less  luminous 
part  the  air  is  combining  with  the  hydrogen  of  the 
hydrocarbon  which  is  being  vaporized  and  disinte¬ 
grated.  Even  the  flame  of  a  candle  or  of  a  burning 
splinter  is  a  miniature  gas-plant,  for  the  solid  or  liquid 
hydrocarbons  are  vaporized  before  being  burned.  Ow¬ 
ing  to  the  incoming  colder  air  at  this  point,  the  flame 
is  not  hot  enough  for  complete  combustion.  The  un¬ 
burned  carbon  particles  rise  in  its  draft  and  become 
heated  to  incandescence,  thus  accounting  for  the 
brighter  portion.  In  cases  of  complete  combustion 
they  are  eventually  oxidized  into  carbon  dioxide  before 
they  are  able  to  escape.  If  a  piece  of  metal  be  held  in 
the  flame,  it  immediately  becomes  covered  with  soot  or 
carbon,  because  it  has  reduced  the  temperature  below 
the  point  at  which  the  chemical  reaction — the  uniting 
of  carbon  with  oxygen — will  continue.  An  ordinary 
flat  gas-flame  of  the  “bats-wing”  type  may  vary  in  tem¬ 
perature  in  its  central  portion  from  300°F.  at  the  bot- 


THE  SCIENCE  OF  LIGHT-PRODUCTION  83 


tom  to  about  3000°F.  at  the  top.  The  central  portion 
lies  between  two  hotter  layers  in  which  the  vertical 
variation  is  not  so  great.  The  brightness  of  the  upper 
portion  is  due  to  incandescent  carbon  formed  in  the 
lower  part. 

When  scientists  learned  by  exploring  flames  that 
brightness  was  due  to  the  radiation  of  light  by  incan¬ 
descent  solid  matter,  the  way  was  open  for  many  ex¬ 
periments.  In  the  early  days  of  gas-lighting  investi¬ 
gations  were  made  to  determine  the  relation  of  illumi¬ 
nating  value  to  the  chemical  constitution  of  the  gas. 
The  results  combined  with  a  knowledge  of  the  necessity 
for  solid  carbon  in  the  flame  led  to  improvements  in  the 
gas  for  lighting  purposes.  Gas  rich  in  hydrocarbons 
which  in  turn  are  rich  in  carbon  is  high  in  illuminating 
value.  Heating-effect  depends  upon  heat-units,  so  the 
rating  of  gas  in  calories  or  other  heat-units  per  cubic 
foot  is  wholly  satisfactory  only  for  gas  used  for  heat¬ 
ing.  The  chemical  constitution  is  a  better  indicator  of 
illuminating  value. 

As  scientific  knowledge  increased,  efforts  were  made 
to  get  solid  matter  into  the  flames  of  light-sources. 
Instead  of  confining  efforts  to  the  carbon  content  of  the 
gas,  solid  materials  were  actually  placed  in  the  flame, 
and  in  this  manner  various  incandescent  burners  were 
developed.  A  piece  of  lime  placed  in  a  hydrogen  flame 
or  that  of  a  Bunsen  burner  is  seen  to  become  hot  and  to 
glow  brilliantly.  By  producing  a  hotter  flame  by 
means  of  the  blowpipe,  in  which  hydrogen  and  oxygen 
are  consumed,  the  piece  of  lime  was  raised  to  a  higher 
temperature  and  a  more  intense  light  was  obtained. 
In  Paris  there  was  a  serious  attempt  at  street-lighting 


84 


ARTIFICIAL  LIGHT 


by  the  use  of  buttons  of  zirconia  heated  in  an  oxygen- 
eoal-gas  flame,  but  it  proved  unsuccessful  owing  to  the 
rapid  deterioration  of  the  buttons.  This  was  the  line 
of  experimentation  which  led  to  the  development  of  the 
lime-light.  The  incandescent  burner  was  widely  em¬ 
ployed,  and  until  the  use  of  electricity  became  common 
the  lime-light  was  the  mainstay  for  the  stage  and  for 
the  projection  of  lantern  slides.  It  is  in  use  even  to¬ 
day  for  some  purposes.  The  origin  of  the  phrase  “in 
the  lime-light  ”  is  obvious.  The  luminous  intensity  of 
the  oxyhydrogen  lime-light  as  used  in  practice  was 
generally  from  200  to  400  candle-power.  The  light  de¬ 
creases  rapidly  as  the  burner  is  used,  if  a  new  surface 
of  lime  is  not  presented  to  the  flame  from  time  to  time. 
At  the  high  temperatures  the  lime  is  somewhat  volatile 
and  the  surface  seems  to  change  in  radiating  power. 
Zirconium  oxide  has  been  found  to  serve  better  than 
lime. 

Improvements  were  made  in  gas-burners  in  order  to 
obtain  hotter  flames  into  which  solid  matter  could  be 
introduced  to  obtain  bright  light.  Many  materials 
were  used,  but  obviously  they  were  limited  to  those  of 
a  fairly  high  melting-point.  Lime,  magnesia,  zirconia, 
and  similar  oxides  were  used  successfully.  If  the 
reader  would  care  to  try  an  experiment  in  verification 
of  this  simple  principle,  let  him  take  a  piece  of  magne¬ 
sium  ribbon  such  as  is  used  in  lighting  for  photography 
and  ignite  it  in  a  Bunsen  flame.  If  it  is  held  carefully 
while  burning,  a  ribbon  of  ash  (magnesia)  will  be  ob¬ 
tained  intact.  Placing  this  in  the  faintly  luminous 
flame,  he  will  be  surprised  at  the  brilliance  of  its  in¬ 
candescence  when  it  has  become  heated.  The  simple 


THE  SCIENCE  OF  LIGHT-PRODUCTION  85 


experiment  indicates  the  possibilities  of  light-produc¬ 
tion  in  this  direction.  Naturally,  metals  of  high  melt¬ 
ing-point  such  as  platinum  were  tried  and  a  network 
of  platinum  wire,  in  reality  a  platinum  mantle,  came 
into  practical  use  in  about  1880.  The  town  of  Nantes 
was  lighted  by  gas-burners  using  these  platinum-gauze 
mantles,  but  the  mantles  were  unsuccessful  owing  to 
their  rapid  deterioration.  This  line  of  experimenta¬ 
tion  finally  bore  fruit  of  immense  value  for  from  it  the 
gas-mantle  evolved. 

A  group  of  so-called  4 Hare-earths,’ r  among  which 
are  zirconia,  thoria,  ceria,  erbia,  and  yttria  (these  are 
oxides  of  zirconium,  etc.)  possess  a  number  of  interest¬ 
ing  chemical  properties  some  of  which  have  been  util¬ 
ized  to  advantage  in  the  development  of  modern  arti¬ 
ficial  light.  They  are  white  or  yellowish-white  oxides 
of  a  highly  refractory  character  found  in  certain  rare 
minerals.  Most  of  them  are  very  brilliant  when  heated 
to  a  high  temperature.  This  latter  feature  is  easily 
explained  if  the  nature  of  light  and  the  radiating  prop¬ 
erties  of  substances  are  considered.  Suppose  pieces  of 
different  substances,  for  example,  glass  and  lime,  are 
heated  in  a  Bunsen  flame  to  the  same  temperature 
which  is  sufficiently  great  to  cause  both  of  them  to  glow. 
Notwithstanding  the  identical  conditions  of  heating,  the 
glass  will  be  only  faintly  luminous,  while  the  piece  of 
lime  will  glow  brilliantly.  The  former  is  a  poor  radi¬ 
ator;  furthermore,  the  lime  radiates  a  relatively 
greater  percentage  of  its  total  energy  in  the  form  of 
luminous  energy. 

The  latter  point  will  become  clearer  if  the  reader  will 
refresh  his  memory  regarding  the  nature  of  light. 


86 


ARTIFICIAL  LIGHT 


Any  luminous  source  such  as  the  sun,  a  candle  flame,  or 
an  incandescent  lamp  is  sending  forth  electromagnetic 
waves  not  unlike  those  used  in  wireless  telegraphy  ex¬ 
cepting  that  they  are  of  much  shorter  wave-length. 
The  eye  is  capable  of  recording  some  of  these  waves  as 
light  just  as  a  receiving  station  is  tuned  to  record  a 
range  of  wave-lengths  of  electromagnetic  energy.  The 
electromagnetic  waves  sent  forth  by  a  light-source  like 
the  sun  are  not  all  visible,  that  is,  all  of  them  do  not 
arouse  a  sensation  of  light.  Those  that  do  comprise 
the  visible  spectrum  and  the  different  wave-lengths  of 
visible  radiant  energy  manifest  themselves  by  arousing 
the  sensations  of  the  various  spectral  colors.  The 
radiant  energy  of  shortest  wave-length  perceptible  by 
the  visual  apparatus  excites  the  sensation  of  violet  and 
the  longest  ones  the  sensation  of  deep  red.  Between 
these  two  extremes  of  the  visible  spectrum,  the  chief 
spectral  colors  are  blue,  green,  yellow,  orange,  and  red 
in  the  order  of  increasing  wave-lengths.  Electro¬ 
magnetic  energy  radiated  by  a  light-source  in  waves  of 
too  great  wave-length  to  be  perceived  by  the  eye  as 
light  is  termed  as  a  class  “ infra-red  radiant  energy.” 
Those  too  short  to  be  perceived  as  light  are  termed  as 
a  class  “ ultraviolet  radiant  energy.”  A  solid  body 
at  a  high  temperature  emits  electro-magnetic  energy  of 
all  wave-lengths,  from  the  shortest  ultra-violet  to  the 
longest  infra-red. 

Another  complication  arises  in  the  variation  in  visi¬ 
bility  or  luminosity  of  energy  of  wave-lengths  within 
the  range  of  the  visible  spectrum.  Obviously,  no 
amount  of  energy  incapable  of  exciting  the  sensation  of 
light  will  be  visible.  The  energy  of  those  wave-lengths 


THE  SCIENCE  OF  LIGHT-PRODUCTION  87 


near  the  ends  of  the  visible  spectrum  will  be  inefficient 
in  producing  light.  That  energy  which  excites  the  sen¬ 
sation  of  yellow-green  produces  the  greatest  luminosity 
per  unit  of  energy  and  is  the  most  efficient  light.  The 
visibility  or  luminous  efficiency  of  radiant  energy  may 
be  ranged  approximately  in  this  manner  according  to 
the  colors  aroused :  yellow-green,  yellow,  green,  orange, 
blue-green,  red,  blue,  deep  red,  violet. 

Newton,  an  English  scientist,  first  described  the  dis¬ 
covery  of  the  visible  spectrum  and  this  is  of  such  funda¬ 
mental  importance  in  the  science  of  light  that  the  first 
paragraph  of  his  original  paper  in  the  “Transactions 
of  the  Royal  Society  of  London”  is  quoted  as  follows: 

In  the  Year  1666.  (at  which  time  I  applied  my  self  to 
the  Grinding  of  Optick  Glasses  of  other  Figures  than 
Spherical)  I  procured  me  a  Triangular  Glass-Prism, 
to  try  therewith  the  celebrated  Phaenomena  of  Colours. 
And  in  order  thereto,  having  darkened  my  Chamber, 
and  made  a  small  Llole  in  mv  Window-Shuts,  to  let  in 
a  convenient  Quantity  of  the  Sun’s  Light,  I  placed  my 
Prism  at  its  Entrance,  that  it  might  be  thereby  re¬ 
fracted  to  the  opposite  Wall.  It  was  at  first  a  very 
pleasing  Divertisement,  to  view  the  vivid  and  intense 
Colours  produced  thereby;  but  after  a  while  applying 
my  self  to  consider  them  more  circumspectly,  I  became 
surprised  to  see  them  in  an  oblong  Form;  which,  ac¬ 
cording  to  the  receiv’d  Law  of  Refractions,  I  expected 
should  have  been  circular.  They  were  terminated  at 
the  Sides  with  streight  Lines,  but  at  the  Ends  the  Decay 
of  Light  was  so  gradual,  that  it  was  difficult  to  deter¬ 
mine  justly  what  was  the  Figure,  yet  they  seemed  Semi¬ 
circular. 

Even  Newton  could  not  have  had  the  faintest  idea  of 


88  ARTIFICIAL  LIGHT 

the  great  developments  which  were  to  be  based  upon 
the  spectrum. 

Now  to  return  to  the  peculiar  property  of  rare-earth 
oxides — namely,  their  unusual  brilliance  when  heated 
in  a  flame — it  is  easy  to  understand  the  reason  for  this. 
For  example,  when  a  number  of  substances  are  heated 
to  the  same  temperature  they  may  radiate  the  same 
amount  of  energy  and  still  differ  considerably  in 
brightness.  Many  substances  are  * 6 selective’ ’  in  their 
absorbing  and  radiating  properties.  One  may  radiate 
more  luminous  energy  and  less  infra-red  energy,  and 
for  another  the  reverse  may  be  true.  The  former 
would  appear  brighter  than  the  latter.  The  scientific 
worker  in  light-production  has  been  searching  for 
such  ‘ 4  selective  ”  radiators  whose  other  properties  are 
satisfactory.  The  rare-earths  possess  the  property  of 
selectivity  and  are  fortunately  highly  refractory. 
Welsbach  used  these  in  his  mantle,  whose  efficiency  is 
due  partly  to  this  selective  property.  Recent  work 
indicates  that  much  higher  efficiencies  of  light-produc¬ 
tion  are  still  attainable  by  the  principles  involved  in 
the  gas-mantle. 

Turning  again  to  flames,  another  interesting  physical 
phenomenon  is  seen  on  placing  solutions  of  different 
chemical  salts  in  the  flame.  For  example,  if  a  piece  of 
asbestos  is  soaked  in  sodium  chloride  (common  salt) 
and  is  placed  in  a  Bunsen  flame,  the  pale-blue  flame 
suddenly  becomes  luminous  and  of  a  yellow  color.  If 
this  is  repeated  with  other  salts,  a  characteristic  color 
will  be  noted  in  each  case.  The  yellow  flame  is  charac¬ 
teristic  of  sodium  and  if  it  is  examined  by  means  of  a 
spectroscope,  a  brilliant  yellow  line  (in  fact,  a  double 


THE  SCIENCE  OF  LIGHT-PBODUCTION  89 


line)  will  be  seen.  This  forms  the  basis  of  spectrum 
analysis  as  applied  in  chemistry. 

Every  element  has  its  characteristic  spectrum  con¬ 
sisting  usually  of  lines,  but  the  complexity  varies  with 
the  elements.  The  spectra  of  elements  also  exhibit 
lines  in  the  ultra-violet  region  which  may  be  studied 
with  a  photographic  plate,  with  a  photo-electric  cell, 
and  by  other  means.  Their  spectral  lines  or  bands 
also  extend  into  the  infra-red  region  and  here  they  are 
studied  by  means  of  the  bolometer  or  other  apparatus 
for  detecting  radiant  energy  by  the  heat  which  it  pro¬ 
duces  upon  being  absorbed.  Spectrum  analysis  is  far 
more  sensitive  than  the  finest  weighing  balance,  for  if 
a  grain  of  salt  be  dissolved  in  a  barrel  of  water  and  an 
asbestos  strip  be  soaked  in  the  water  and  held  in  a 
Bunsen  flame,  the  yellow  color  characteristic  of  sodium 
will  be  detectable.  A  wonderful  example  of  the  possi¬ 
bilities  of  this  method  is  the  discovery  of  helium  in  the 
sun  before  it  was  found  on  earth!  Its  spectral  lines 
were  detected  in  the  sun’s  spectrum  and  could  not  be 
accounted  for  by  any  known  element.  However,  it 
should  be  stated  that  the  spectrum  of  an  element  differs 
generally  with  the  manner  obtained.  The  electric 
spark,  the  arc,  the  electric  discharge  in  a  vacuum  tube, 
and  the  flame  are  the  means  usually  employed. 

The  spectrum  has  been  dwelt  upon  at  some  length 
because  it  is  of  great  importance  in  light-production 
and  probably  will  figure  strongly  in  future  develop¬ 
ments.  Although  in  lighting  little  use  has  been  made 
of  the  injection  of  chemical  salts  into  ordinary  flames, 
it  appears  certain  that  such  developments  would  have 
arisen  if  electric  illuminants  had  not  entered  the  field. 


90 


ARTIFICIAL  LIGHT 


However,  the  principle  lias  been  applied  with  great 
success  in  arc-lamps.  In  the  first  arc-lamps  plain 
carbon  electrodes  were  used,  but  in  some  of  the  latest 
carbon-arcs,  electrodes  of  carbon  impregnated  with 
various  salts  are  employed.  For  example,  calcium 
fluoride  gives  a  brilliant  yellow  light  when  used  in  the 
carbons  of  the  “flame”  arc.  These  are  described  in 
detail  later. 

Following  this  principle  of  light-production  the 
vacuum  tubes  were  developed.  Crookes  studied  the 
light  from  various  gases  by  enclosing  them  in  a  tube 
which  was  pumped  out  until  a  low  vacuum  was  pro¬ 
duced.  On  connecting  a  high  voltage  to  electrodes  in 
each  end,  an  electrical  discharge  passed  through  the 
residual  gas  making  it  luminous.  The  different  gases 
show  their  characteristic  spectra  and  their  desirability 
as  light-producers  is  at  once  evident. 

However,  the  most  general  principle  of  light-produc¬ 
tion  at  the  present  time  is  the  radiation  of  bodies  by 
virtue  of  their  temperature.  If  a  piece  of  wire  be 
heated  by  electricity,  it  will  become  very  hot  before  it 
becomes  luminous.  At  this  temperature  it  is  emitting 
only  invisible  infra-red  energy  and  has  an  efficiency  of 
zero  as  a  producer  of  light.  As  it  becomes  hotter  it 
begins  to  appear  red,  but  as  its  temperature  is  raised 
it  appears  orange,  until  if  it  could  be  heated  to  the  tem¬ 
perature  of  the  sun,  about  10,000° F.,  it  would  appear 
white.  All  this  time  its  luminous  efficiency  is  increas¬ 
ing,  because  it  is  radiating  not  only  an  increasing  per¬ 
centage  of  visible  radiant  energy  but  an  increasing 
amount  of  the  most  effective  luminous  energy.  But 
even  when  it  appears  white,  a  large  amount  of  the 


THE  SCIENCE  OF  LIGHT-PRODUCTION  91 


energy  which  it  radiates  is  invisible  infra-red  and  ultra¬ 
violet,  which  are  ineffective  in  producing  light,  so  at 
best  the  substance  at  this  high  temperature  is  ineffi¬ 
cient  as  a  light-producer. 

In  this  branch  of  the  science  of  light-production  sub¬ 
stances  are  sought  not  only  for  their  high  melting- 
point,  but  for  their  ability  to  radiate  selectively  as 
much  visible  energy  as  possible  and  of  the  most  lumi¬ 
nous  character.  However,  at  best  the  present  method 
of  utilizing  the  temperature  radiation  of  hot  bodies  has 
limitations. 

The  luminous  efficiencies  of  light-sources  to-day  are 
still  very  low,  but  great  advances  have  been  made  in  the 
past  half-century.  There  must  be  some  radical  de¬ 
partures  if  the  efficiency  of  light-production  is  to  reach 
a  much  higher  figure.  A  good  deal  has  been  said 
of  the  firefly  and  of  phosphorescence.  These  light- 
sources  appear  to  emit  only  visible  energy  and,  there¬ 
fore,  are  efficient  as  radiators  of  luminous  radiant 
energy.  But  much  remains  to  be  unearthed  concerning 
them  before  they  will  be  generally ‘applicable  to  light¬ 
ing.  If  ultra-violet  radiation  is  allowed  to  impinge 
upon  a  phosphorescent  material,  it  will  glow  with  a 
considerable  brightness  but  will  be  cool  to  the  touch. 
A  substance  of  the  same  brightness  by  virtue  of  its 
temperature  would  be  hot;  hence  phosphorescence  is 
said  to  be  “cold”  light. 

An  acquaintance  with  certain  terms  is  necessary  if 
the  reader  is  to  understand  certain  parts  of  the  text. 
The  early  candle  gradually  became  a  standard,  and  uni¬ 
form  candles  are  still  satisfactory  standards  where 
high  accuracy  is  not  required.  Their  luminous  in- 


Q9 

«  J  m i 


ARTIFICIAL  LIGHT 


tensity  and  illuminating'  value  became  units  just  as  the 
foot  was  arbitrarily  adopted  as  a  unit  of  length.  The 
intensity  of  other  light-sources  was  represented  in 
terms  of  the  number  of  candles  or  fraction  of  a  candle 
which  gave  the  same  amount  of  light.  But  the  lumi¬ 
nous  intensity  of  the  candle  was  taken  only  in  the  hori¬ 
zontal  direction.  In  the  same  manner  the  luminous 
intensities  of  light-sources  until  a  short  time  ago  were 
expressed  in  candles  as  measured  in  a  certain  direction. 
Incandescent  lamps  were  rated  in  terms  of  mean  hori¬ 
zontal  candles,  which  would  be  satisfactory  if  the 
luminous  intensity  were  the  same  in  all  directions,  but 
it  is  not.  Therefore,  the  candle-power  in  one  direction 
does  not  give  a  measure  of  the  total  light-output. 

If  a  source  of  light  has  a  luminous  intensity  of  one 
candle  in  all  directions,  the  illumination  at  a  distance 
of  one  foot  in  any  direction  is  said  to  be  a  foot-candle. 
This  is  the  unit  of  illumination  intensity.  A  lumen 
is  the  quantity  of  light  which  falls  on  one  square  foot 
if  the  intensity  of  illumination  is  one  foot-candle.  It 
is  seen  that  the  area  of  a  sphere  with  a  radius  of  one 
foot  is  4tt  or  12.57  square  feet;  therefore,  a  light-source 
having  a  luminous  intensity  of  one  candle  in  all  direc¬ 
tions  emits  12.57  lumens.  This  is  the  satisfactory  unit, 
for  it  measures  total  quantity  of  light,  and  luminous 
efficiencies  may  be  expressed  in  terms  of  lumens  per 
watt,  lumens  per  cubic  foot  of  gas  per  hour,  etc. 

Of  course,  the  efficiencies  of  light-sources  are  usually 
of  interest  to  the  consumer  if  they  are  expressed  in 
terms  of  cost.  But  from  a  practical  point  of  view 
there  are  many  elements  which  combine  to  make 


THE  SCIENCE  OF  LIGHT-PRODUCTION  93 


another  important  factor,  namely,  satisfactoriness. 
Therefore,  the  efficiency  of  artificial  lighting  from  the 
standpoint  of  the  consumer  should  be  the  ratio  of 
satisfactoriness  to  cost.  However,  the  scientist  is  in¬ 
terested  chiefly  in  the  efficiency  of  the  light-source 
which  may  be  expressed  in  lumens  per  watt,  or  the 
amount  of  light  obtained  from  a  given  rate  of  consump¬ 
tion  or  of  emission  of  energy.  This  method  of  rating 
light-sources  penalizes  those  radiating  considerable 
„  energy  which  does  not  produce  the  sensation  of  light  or 
which  at  best  is  of  wave-lengths  that  are  inefficient  in 
this  respect.  That  radiant  energy  which  is  wholly  of  a 
wave-length  of  maximum  visibility,  or,  in  other  words, 
excites  the  sensation  of  yellow-green,  is  the  most  effi¬ 
cient  in  producing  luminous  sensation.  Of  course,  no 
illuminants  are  available  which  approach  this  theoreti¬ 
cal  ideal  and  it  is  not  likely  that  this  would  be  a  prac¬ 
tical  ideal.  Under  monochromatic  yellow-green  light 
the  magical  drapery  of  color  would  disappear  and  the 
surroundings  would  be  a  monochrome  of  shades  of  this 
hue.  Having  no  colors  with  which  to  contrast  this 
color,  the  world  would  be  colorless.  This  should  be 
obvious  when  it  is  considered  that  an  object  which  is 
red  under  an  illuminant  containing  all  colors  such  as 
sunlight  would  be  black  or  dark  gray  under  monochro¬ 
matic  yellow-green  light.  The  red  under  present  con¬ 
ditions  is  kept  alive  by  contrast  with  other  colors,  be¬ 
cause  the  latter  live  by  virtue  of  the  fact  that  most  of 
our  present  illuminants  contain  their  hues.  It  is  as¬ 
sumed  that  the  reader  knows  that  a  red  object,  for  ex¬ 
ample,  appears  red  because  it  reflects  (or  transmits) 


94 


ARTIFICIAL  LIGHT 


red  rays  and  absorbs  the  other  rays  in  the  illuminant. 
In  other  words,  color  is  due  to  selective  absorption,  re¬ 
flection,  or  transmission. 

Perhaps  the  ideal  illuminant,  which  is  most  generally 
satisfactory  for  general  activities,  is  a  white  light  cor¬ 
responding  to  noon  sunlight.  If  this  is  chosen  as  the 
scientific  ideal,  the  illuminants  of  the  present  time  are 
much  more  “  efficient  ”  than  if  the  most  efficient  light  is 
the  ideal. 

The  luminous  efficiency  of  the  radiant  energy  most 
efficient  in  producing  the  sensation  of  light  (yellow- 
green)  is  about  625  lumens  per  watt.  That  is,  if 
energy  of  this  wave-length  alone  were  radiated  by  a 
hypothetical  light-source,  each  watt  would  produce  625 
lumens.  The  luminous  efficiency  of  the  most  efficient 
white  light  is  about  265  lumens  per  watt;  in  other 
words,  if  a  hypothetical  light-source  radiated  energy 
of  only  the  visible  wave-lengths  and  in  proportions  to 
produce  the  sensation  of  white,  each  watt  would  pro¬ 
duce  265  lumens.  If  such  a  white  light  were  obtained 
by  pure  temperature  radiation — that  is,  by  a  normal 
radiator  at  a  temperature  of  1 0,000 °F.,  which  is  imprac¬ 
ticable  at  present — the  luminous  efficiency  would  be 
about  100  lumens  per  watt.  The  normal  radiator 
which  emits  energy  by  virtue  of  its  temperature  with¬ 
out  selectively  radiating  more  or  less  energy  in  any 
part  of  the  spectrum  than  indicated  by  the  theoretical 
radiation  laws  is  called  a  u  black-body  ’  ’  or  normal  ra¬ 
diator.  Modern  illuminants  have  luminous  efficiencies 
ranging  from  5  to  30  lumens  per  watt,  so  it  is  seen  that 
much  is  to  be  done  before  the  limiting  efficiencies  are 
reached. 


THE  SCIENCE  OF  LIGHT-PRODUCTION  95 


The  amount  of  light  obtained  from  various  gas- 
burners  for  each  cubic  foot  of  gas  consumed  per  hour 
varies  for  open  gas-flames  from  5  to  30  lumens;  for 
Argand  burners  from  35  to  40  lumens ;  for  regenerative 
lamps  from  50  to  75  lumens;  and  for  gas-mantles  from 
200  to  250  lumens. 

In  the  development  of  light-sources,  of  course,  any 
harmful  effects  of  gases  formed  by  burning  or  chemical 
action  must  be  avoided.  Some  of  the  fumes  from  arcs 
are  harmful,  but  no  commercial  arc  appears  to  be  dan¬ 
gerous  when  used  as  it  is  intended  to  be  used.  Gas- 
burners  rob  the  atmosphere  of  oxygen  and  vitiate  it 
with  gases,  which,  however,  are  harmless  if  combustion 
is  complete.  That  adequate  ventilation  is  necessary 
where  oxygen  is  being  consumed  is  evident  from  the 
data  presented  by  authorities  on  hygiene.  A  standard 
candle  when  burning  vitiates  the  air  in  a  room  almost 
as  much  as  an  adult  person.  An  ordinary  kerosene 
lamp  vitiates  the  atmosphere  as  much  as  a  half-dozen 
persons.  An  ordinary  single  mantle  burner  causes  as 
much  vitiation  as  two  or  three  persons. 

In  order  to  obtain  a  bird’s-eye  view  of  progress  in 
light-production,  the  following  table  of  relative  lumi¬ 
nous  efficiencies  of  several  light-sources  is  given  in 
round  numbers.  These  efficiencies  are  in  terms  of  the 
most  efficient  (yellow-green)  light. 

Efficiency 
in  per  cent. 


Sperm-candle .  0.02 

Open  gas-flame  .  .04 

Incandescent  gas-mantle  .  .19 

Carbon  filament  lamp .  .05 

Vacuum  Mazda  lamp .  1.3 


96 


ARTIFICIAL  LIGHT 


Efficiency 
in  per  cent. 


Gas-filled  Mazda  lamp .  2  to  3 

Arc-lamps  .  2  to  7 

White  light  radiated  by  “black-body ” .  16 

Most  efficient  white  light .  40 

Firefly  .  95 

Most  efficient  light  (yellow-green)  .  100 


The  luminous  efficiency  of  a  light-source  is  distin¬ 
guished  from  that  of  a  lamp.  The  former  is  the  ratio 
of  the  light  produced  to  the  amount  of  energy  radiated 
by  the  light-source.  The  latter  is  the  ratio  of  the  light 
produced  to  the  total  amount  of  energy  consumed  by 
the  device.  In  other  words,  the  luminous  efficiency  of 
a  lamp  is  less  than  that  of  the  light-source  because  the 
consumption  of  energy  in  other  parts  of  the  lamp  be¬ 
sides  the  light-source  are  taken  into  account.  These 
additional  losses  are  appreciable  in  the  mechanisms  of 
arc-lamps  but  are  almost  negligible  in  vacuum  incan¬ 
descent  filament  lamps.  They  are  unknown  for  the 
firefly,  so  that  its  luminous  efficiency  only  as  a  light- 
source  can  be  determined.  Its  efficiency  as  a  lighting- 
plant  may  be  and  perhaps  is  rather  low. 


VIII 

MODERN  GAS-LIGHTING 

As  has  been  seen,  the  lighting  industry,  as  a  public 
service,  was  born  in  London  about  a  century  ago  and 
companies  to  serve  the  public  were  organized  on  the 
Continent  shortly  after.  From  this  early  beginning 
gas-light  remained  for  a  long  time  the  only  illuminant 
supplied  by  a  public-service  company.  It  has  been  seen 
that  throughout  the  ages  little  advance  was  made  in 
lighting  until  oil-lamps  were  improved  by  Argand  in 
the  eighteenth  century.  Candles  and  open-flame  oil- 
lamps  were  in  use  when  the  Pyramids  were  built  and 
these  were  common  until  the  approach  of  the  nine¬ 
teenth  century.  In  fact,  several  decades  passed  after 
the  first  gas-lighting  was  installed  before  this  form  of 
lighting  began  to  displace  the  improved  oil-lamps  and 
candles.  It  was  not  until  about  1850  that  it  began  to 
invade  the  homes  of  the  middle  and  poorer  classes. 
During  the  first  half  of  the  nineteenth  century  the  total 
light  in  an  average  home  was  less  than  is  now  obtained 
from  a  single  light-source  used  in  residences;  still,  the 
total  cost  of  lighting  a  residence  has  decreased  con¬ 
siderably.  If  the  social  and  industrial  activities  of 
mankind  are  visualized  for  these  various  periods  in 
parallel  with  the  development  of  artificial  lighting,  a 
close  relation  is  evident.  Did  artificial  light  advance 
merely  hand  in  hand  with  science,  invention,  commerce, 

and  industry,  or  did  it  illuminate  the  pathway? 

97 


98 


ARTIFICIAL  LIGHT 


Although  gas-lighting  was  born  in  England,  it  soon 
began  to  receive  attention  elsewhere.  In  1815  the  first 
attempt  to  provide  a  gas-works  in  America  was  made 
in  Philadelphia;  but  progress  was  slow,  with  the  result 
that  Baltimore  and  New  York  led  in  the  erection  of 
gas-works.  There  are  on  record  many  protests 
against  proposals  which  meant  progress  in  lighting. 
These  are  amusing  now,  but  they  indicate  the  inertia 
of  the  people  in  such  matters.  When  Bollman  was 
projecting  a  plan  for  lighting  Philadelphia  by  means 
of  piped  gas,  a  group  of  prominent  citizens  submitted 
a  protest  in  1833  which  aimed  to  show  that  the  conse¬ 
quences  of  the  use  of  gas  were  appalling.  But  this 
protest  failed  and  in  1835  a  gas-plant  was  founded  in 
Philadelphia.  Thus  gas-lighting,  which  to  Sir  Walter 
Scott  was  a  “pestilential  innovation”  projected  by  a 
madman,  weathered  its  early  difficulties  and  grew  to 
be  a  mighty  industry.  Continued  improvements  and 
increasing  output  not  only  altered  the  course  of  civ¬ 
ilization  by  increased  and  adequate  lighting  but  they 
reduced  the  cost  of  lighting  over  the  span  of  the  nine¬ 
teenth  century  to  a  small  fraction  of  its  initial  cost. 

Think  of  the  city  of  Philadelphia  in  1800,  with  a 
population  of  about  fifty  thousand,  dependent  for  its 
lighting  wholly  upon  candles  and  oil-lamps!  Wash¬ 
ington’s  birthday  anniversary  was  celebrated  in  1817 
with  a  grand  ball  attended  by  five  hundred  of  the  elite. 
An  old  report  of  the  occasion  states  that  the  room  was 
lighted  by  two  thousand  wax-candles.  The  cost  of  this 
lighting  was  a  hundred  times  the  cost  of  as  much  light 
for  a  similar  occasion  at  the  present  time.  Can  one 
imagine  the  present  complex  activities  of  a  city  like 


MODERN  GAS-LIGHTING 


99 


Philadelphia  with  nearly  two  million  inhabitants  to 
exist  under  the  lighting  conditions  of  a  century  ago? 
To-day  there  are  more  than  fifty  thousand  street  lamps 
in  the  city — one  for  each  inhabitant  of  a  century  ago. 
Of  these  street  lamps  about  twenty-five  thousand  burn 
gas.  This  single  instance  is  representative  of  gas¬ 
lighting  which  initiated  the  4 ‘ light  age”  and  nursed  it 
through  the  vicissitudes  of  youth.  The  consumption 
of  gas  has  grown  in  the  United  States  during  this  time 
to  three  billion  cubic  feet  per  day.  For  strictly  illu¬ 
minating  purposes  in  1910  nearly  one  hundred  billion 
cubic  feet  were  used.  This  country  has  been  blessed 
with  large  supplies  of  natural  gas;  but  as  this  fails 
new  oil-fields  are  constantly  being  discovered,  so  that 
as  far  as  raw  materials  are  concerned  the  future  of 
gas-lighting  is  assured  for  a  long  time  to  come. 

The  advent  of  the  gas-mantle  is  responsible  for  the 
survival  of  gas-lighting,  because  when  it  appeared  elec¬ 
tric  lamps  had  already  been  invented.  These  were  des¬ 
tined  to  become  the  formidable  light-sources  of  the 
approaching  century  and  without  the  gas-mantle  gas¬ 
lighting  would  not  have  prospered.  Auer  von  Wels- 
bach  was  conducting  a  spectroscopic  study  of  the  rare- 
earths  when  he  was  confronted  with  the  problem  of 
heating  these  substances.  He  immersed  cotton  in  solu¬ 
tions  of  these  salts  as  a  variation  of  the  regular  means 
for  studying  elements  by  injecting  them  into  flames. 
After  burning  the  cotton  he  found  that  he  had  a  replica 
of  the  original  fabric  composed  of  the  oxide  of  the 
metal,  and  this  glowed  brilliantly  when  left  in  the 
flame. 

This  gave  him  the  idea  of  producing  a  mantle  for 


100 


ARTIFICIAL  LIGHT 


illuminating  purposes  and  in  1885  he  placed  such  a 
mantle  in  commercial  use.  His  first  mantles  were  un¬ 
satisfactory,  but  they  were  improved  in  1886  by  the 
use  of  thoria,  an  oxide  of  thorium,  in  conjunction  with 
other  rare-earth  oxides.  His  mantle  was  now  not  only 

•r 

stronger  but  it  gave  more  light.  Later  he  greatly  im¬ 
proved  the  mantles  by  purifying  the  oxides  and  finally 
achieved  his  great  triumph  by  adding  a  slight  amount 
of  ceria,  an  oxide  of  cerium.  Welsbach  is  deserving  of 
a  great  deal  of  credit  for  his  extensive  work,  which 
overcame  many  difficulties  and  finally  gave  to  the  world 
a  durable  mantle  that  greatly  increased  the  amount  of 
light  previously  obtainable  from  gas. 

The  physical  characteristics  of  a  mantle  depend  upon 
the  fabric  and  upon  the  rare-earths  used.  It  must  not 
shrink  unduly  when  burned,  and  the  ash  should  remain 
porous.  It  has  been  found  that  a  mantle  in  which 
thoria  is  used  alone  is  a  poor  light-source,  but  that 
when  a  small  amount  of  ceria  is  added  the  mantle  glows 
brilliantly.  By  experiment  it  was  determined  that  the 
best  proportions  for  the  rare-earth  content  are  one 
part  of  ceria  and  ninety-nine  parts  of  thoria.  Greater 
or  less  proportions  of  ceria  decreased  the  light-output. 
The  actual  percentage  of  these  oxides  in  the  ash  of  the 
mantle  is  about  10  per  cent.,  making  the  content  of 
ceria  about  one  part  in  one  thousand. 

Mantles  are  made  by  knitting  cylinders  of  cotton  or 
of  other  fiber  and  soaking  these  in  a  solution  of  the 
nitrates  of  cerium  and  thorium.  One  end  of  the 
cylinder  is  then  sewed  together  with  asbestos  thread, 
Avhich  also  provides  the  loop  for  supporting  the  man¬ 
tle  over  the  burner.  After  the  mantle  has  dried  in 


MODERN  GAS-LIGHTING 


101 


proper  form,  it  is  burned;  the  organic  matter  disap¬ 
pears  and  the  nitrates  are  converted  into  oxides. 
After  this  “burning  off”  has  been  accomplished  and 
any  residual  blackening*  is  removed,  the  mantle  is 
dipped  into  collodion,  which  strengthens  it  for  ship¬ 
ping  and  handling.  The  collodion  is  a  solution  of  gun¬ 
cotton  in  alcohol  and  ether  to  which  an  oil  such  as  cas¬ 
tor-oil  has  been  added  to  prevent  excessive  shrinkage 
on  drying. 

The  materials  and  structure  of  the  fabric  of  mantles 
have  been  subjected  to  much  study.  Cotton  was  first 
used;  then  ramie  fibers  were  introduced.  The  ramie 
mantle  was  found  to  possess  a  greater  life  than  the 
cotton  mantle.  Later  the  mantles  were  mercerized  by 
immersion  in  ammonia-water  and  this  process  yielded 
a  stronger  material.  The  latest  development  is  the 
use  of  an  Artificial  silk  as  the  base  fabric,  which  re¬ 
sults  in  a  mantle  superior  to  previous  mantles  in 
strength,  flexibility,  permanence  of  form,  and  perma¬ 
nence  of  luminous  property.  This  artificial  silk  man¬ 
tle  will  permit  of  handling  even  after  it  has  been  in 
use  for  several  hundred  hours.  This  great  advance 
appears  to  be  due  to  the  fact  that  after  the  artificial- 
silk  fibers  have  been  burned  off,  the  fibers  are  solid 
and  continuous  instead  of  porous  as  in  previous 
mantles. 

The  color-value  of  the  light  from  mantles  may  be 
varied  considerably  by  altering  the  proportions  of  the 
rare-earths.  The  yellowness  of  the  light  has  been 
traced  to  ceria,  so  by  varying  the  proportions  of  ceria, 
the  color  of  the  light  may  be  influenced. 

The  inverted  mantle  introduced  greater  possibilities 


102 


ARTIFICIAL  LIGHT 


into  gas-lighting.  The  light  could  be  directed  down¬ 
ward  with  ease  and  many  units  such  as  inverted  bowls 
were  developed.  In  fact,  the  lighting-fixtures  and  the 
lighting-effects  obtainable  kept  pace  with  those  of  elec¬ 
tric  lighting,  notwithstanding  the  greater  difficulties 
encountered  by  the  designer  of  gas-lighting  fixtures. 
Many  problems  were  encountered  in  designing  an  in¬ 
verted  burner  operating  on  the  Bunsen  principle,  but 
they  were  finally  satisfactorily  solved.  In  recent  years 
a  great  deal  of  study  has  been  given  to  the  efficiency  of 
gas-burners,  with  the  result  that  a  high  level  of  de¬ 
velopment  has  been  reached. 

Several  methods  of  electrical  ignition  have  been 
evolved  which  in  general  employ  the  electric  spark. 
Electrical  ignition  and  developments  of  remote  con¬ 
trol  have  added  great  improvements  especially  to 
street-lighting  by  means  of  gas.  Gas-valves  for  re¬ 
mote  control  are  actuated  by  gas  pressure  and  by  elec¬ 
tromagnets.  In  general,  the  gas-lighting  engineers 
have  kept  pace  marvelously  with  electric  lighting,  when 
their  handicaps  are  considered. 

Various  types  of  burners  have  appeared  which 
aimed  to  burn  more  gas  in  a  given  time  under  a  mantle 
and  thereby  to  increase  the  output  of  light.  These  led 
to  the  development  of  the  pressure  system  in  which 
the  pressure  of  gas  was  at  first  several  times  greater 
than  usual.  The  gas  is  fed  into  the  mixing  tube  under 
this  higher  pressure  in  a  manner  which  also  draws  in 
an  adequate  amount  of  air.  In  this  way  the  combus¬ 
tion  at  the  burner  is  forced  beyond  the  point  reached 
with  the  usual  pressure.  Ordinary  gas  pressure  is 
equal  to  that  of  a  few  inches  of  water,  but  high-pres- 


MODERN  GAS-LIGHTING 


103 


sure  systems  employ  pressures  as  great  as  sixty  inches 
of  water.  Under  this  high-pressure  system,  mantle- 
burners  yield  as  high  as  500  lumens  per  cubic  foot  of 
gas  per  hour. 

The  fuels  for  gas-lighting  are  natural  gas,  carbureted 
water-gas,  and  coal-gas  obtained  by  distilling  coal,  but 
there  are  different  methods  of  producing  the  artificial 
gases.  Coal-gas  is  produced  analytically  by  distilling 
certain  kinds  of  coal,  but  water-gas  and  producer-gas 
are  made  synthetically  by  the  action  of  several  con¬ 
stituents  upon  one  another.  Carbureted  water-gas  is 
made  from  fixed  carbon,  steam,  and  oil  and  also  from 
steam  and  oil.  Producer-gas  is  made  by  the  action  of 
steam  or  air  or  both  upon  fixed  carbon.  Water-gas 
made  from  steam  and  oil  is  usually  limited  to  those 
places  where  the  raw  materials  are  readily  available. 
The  composition  of  a  gas  determines  its  heating  and 
illuminating  values,  and  constituents  favorable  to  one 
are  not  necessarily  favorable  to  the  other.  Coal-gas 
usually  is  of  lower  illuminating  value  than  carbureted 
water-gas.  It  contains  more  hydrogen,  for  example, 
than  water-gas  and  it  is  well  known  that  hydrogen 
gives  little  light  on  burning. 

It  has  been  seen  in  a  previous  chapter  that  the  dis¬ 
tillation  of  gas  from  coal  for  illuminating  purposes  be¬ 
gan  in  the  latter  part  of  the  eighteenth  century.  From 
this  beginning  the  manufacture  of  coal-gas  has  been 
developed  to  a  great  and  complex  industry.  The 
method  is  essentially  destructive  distillation.  The  coal 
is  placed  in  a  retort  and  when  it  reaches  a  temperature 
of  about  700° F.  through  heating  by  an  outside  fire,  the 
coal  begins  to  fuse  and  hydrocarbon  vapors  begin  to 


104 


ARTIFICIAL  LIGHT 


emanate.  These  are  generally  paraffins  and  olefins. 
As  the  temperature  increases,  these  hydrocarbons  be¬ 
gin  to  be  affected.  The  chemical  combinations  which 
have  long  existed  are  broken  up  and  there  are  rear¬ 
rangements  of  the  atoms  of  carbon  and  hydrogen.  The 
actual  chemical  reactions  become  very  complex  and  are 
somewhat  shrouded  in  uncertainty.  In  this  last  stage 
the  illuminating  and  heating  values  of  the  gas  are 
determined.  Usually  about  four  hours  are  allowed  for 
the  complete  distillation  of  the  gaseous  and  liquid  prod¬ 
ucts  from  a  charge  of  coal.  Many  interesting  chemi¬ 
cal  problems  arise  in  this  process  and  the  influences  of 
temperature  and  time  cannot  be  discussed  within  the 
scope  of  this  book.  Besides  the  coal-gas,  various  by¬ 
products  are  obtained  depending  upon  the  raw  ma¬ 
terials,  upon  the  procedure,  and  upon  the  market. 

After  the  coal-gas  is  produced  it  must  be  purified 
and  the  sulphureted  hydrogen  at  least  must  be  re¬ 
moved.  One  method  of  accomplishing  this  is  by  wash¬ 
ing  the  gas  with  water  and  ammonia,  which  also  re¬ 
moves  some  of  the  carbon  dioxide  and  hydrocyanic 
acid.  Various  other  undesirable  constituents  are  re¬ 
moved  by  chemical  means,  depending  upon  the  condi¬ 
tions.  The  purified  gas  is  now  delivered  to  the  gas¬ 
holder  ;  but,  of  course,  all  this  time  the  pressure  is  gov¬ 
erned,  in  order  that  the  pressure  in  the  mains  will  be 
maintained  constant. 

Much  attention  has  been  given  to  the  enrichment  of 
gas  for  illuminating  purposes;  that  is,  to  produce  a 
gas  of  high  illuminating  value  from  cheap  fuel  or  by 
inexpensive  processes.  This  has  been  done  by  decom¬ 
posing  the  tar  obtained  during  the  distillation  of  coal 


MODERN  GAS-LIGHTING 


105 


and  adding  these  gases  to  the  coal-gas ;  by  mixing  car¬ 
bureted  water-gas  with  coal-gas;  by  carbureting  in¬ 
ferior  coal-gases;  and  by  mixing  oil-gas  with  inferior 
coal-gas. 

Water-gas  is  of  low  illuminating  value,  but  after  it 
is  carbureted  it  burns  with  a  brilliant  flame.  The  wa¬ 
ter-gas  is  made  by  raising  the  temperature  of  the  fuel 
bed  of  hard  coal  or  coke  by  forced  air,  which  is  then 
cut  off,  while  steam  is  passed  through  the  incandescent 
fuel.  This  yields  hydrogen  and  carbon  monoxide.  To 
make  carbureted  water-gas,  oil-gas  is  mixed  with  it, 
the  latter  being  made  by  heating  oil  in  retorts. 

A  great  many  kinds  of  gas  are  made  which  are  de¬ 
termined  by  the  requirements  and  the  raw  materials 
available.  The  amount  of  illuminating  gas  yielded  by 
a  ton  of  fuel,  of  course,  varies  with  the  method  of  man¬ 
ufacture,  with  the  raw  material,  and  with  the  use  to 
which  the  fuel  is  to  be  put.  The  production  of  coal- 
gas  per  ton  of  coal  is  of  the  order  of  magnitude  of  10,- 
000  cubic  feet.  A  typical  yield  by  weight  of  a  coal- 
gas  retort  is, 

10,000  cubic  feet  of  gas .  17  per  cent. 


coke  . 

tar  . . 

ammoniacal  liquid 


The  coke  is  not  pure  carbon  but  contains  the  non¬ 
volatile  minerals  which  will  remain  as  ash  when  the 
coke  is  burned,  just  as  if  the  original  coal  had  been 
burned.  On  the  crown  of  the  retort  used  in  coal-gas 
production,  pure  carbon  is  deposited.  This  is  used  for 
electric-arc  carbons  and  for  other  purposes.  From 


106 


ARTIFICIAL  LIGHT 


the  tar  many  products  are  derived  such  as  aniline  dyes, 
benzene,  carbolic  acid,  picric  acid,  napthalene,  pitch, 
anthracene,  and  saccharin. 

A  typical  analysis  of  the  gas  distilled  from  coal  is 
very  approximately  as  follows, 


Hydrocarbons .  40  per  cent. 

Hydrogen  .  50  “  “ 

Carbon  monoxide  .  4  “ 

Nitrogen  .  4  “  “ 

Carbon  dioxide  .  1  “  “ 

Various  other  gases .  1  “ 


It  is  seen  that  illuminating  gas  is  not  a  definite  com¬ 
pound  but  a  mixture  of  a  number  of  gases.  The  pro¬ 
portion  of  these  is  controlled  in  so  far  as  possible  in 
order  to  obtain  illuminating  value  and  some  of  them  are 
reduced  to  very  small  percentages  because  they  are 
valueless  as  illuminants  or  even  harmful.  The  con¬ 
stituents  are  seen  to  consist  of  light-giving  hydrocar¬ 
bons,  of  gases  which  yield  chiefly  heat,  and  of  impuri¬ 
ties.  The  chief  hydrocarbons  found  in  illuminating 
gas  are, 


ethylene 

cjr4 

crotonylene 

c4h. 

propylene 

c3h. 

benzene 

c,h. 

butylene 

c4hs 

toluene 

C,Ha 

amylene 

c5h10 

xylene 

CSH10 

acetylene 

c2h2 

methane 

C  h4 

allylene 

c3h4 

ethane 

c2h„ 

A  gas  which  has  played  a  prominent  part  in  lighting 
is  acetylene,  produced  by  the  interaction  of  water  and 
calcium  carbide.  No  other  gas  easily  produced  upon  a 
commercial  scale  yields  as  much  light,  volume  for  vol- 


MODERN  GAS-LIGHTING 


107 


ume,  as  acetylene.  It  has  the  great  advantage  of  being 
easily  prepared  from  raw  material  whose  yield  of  gas 
is  considerably  greater  for  a  given  amount  than  the 
raw  materials  which  are  used  in  making  other  illumi¬ 
nating  gases.  The  simplicity  of  the  manufacture  of 
acetylene  from  calcium  carbide  and  water  gives  to  this 
gas  a  great  advantage  in  some  cases.  It  has  served  for 
individual  lighting  in  houses  and  in  other  places  where 
gas  or  electric  service  was  unavailable.  Where  space 
is  limited  it  also  had  an  advantage  and  was  adopted 
to  some  extent  on  automobiles,  motor-boats,  ships, 
lighthouses,  and  railway  cars  before  electric  lighting 
was  developed  for  these  purposes. 

The  color  of  the  acetylene  flame  is  satisfactory  and  it 
is  extremely  brilliant  compared  with  most  flames.  An 
interesting  experiment  is  found  in  placing  a  spark-gap 
in  the  flame  and  sending  a  series  of  sparks  across  it. 
If  the  conditions  are  proper  the  flame  will  became  very 
much  brighter.  When  the  gas  issues  from  a  proper 
jet  under  sufficient  pressure,  the  flame  is  quite  steady. 
Its  luminous  efficiency  gives  it  an  advantage  over  other 
open  gas-flames  in  lighting  rooms,  because  for  the  same 
amount  of  light  it  vitiates  the  air  and  exhausts  the 
oxygen  to  a  less  degree  than  the  others.  Of  course,  in 
these  respects  the  gas-mantle  is  superior. 

The  reaction  which  takes  place  when  water  and  cal¬ 
cium  carbide  are  brought  together  is  a  double  decom¬ 
position  and  is  represented  by, 

CaC2  +  HoO  -  C2H2  +  CaO 

It  will  be  seen  that  the  products  are  acetylene  gas  and 
calcium  oxide  or  lime.  The  lime,  being  hydroscopic 


108 


ARTIFICIAL  LIGHT 


and  being  in  the  presence  of  water  or  water-vapor  in 
the  acetylene  generator,  really  becomes  calcium  hy¬ 
droxide  Ca(OH)2,  commonly  called  slaked  lime.  If 
there  are  impurities  in  the  calcium  carbide,  it  is  some¬ 
times  necessary  to  purify  the  gas  before  it  may  be 
safely  used  for  interior  lighting. 

The  burners  and  mantles  used  in  acetylene  lighting 
are  essentially  the  same  as  those  for  other  gas-lighting, 
excepting,  of  course,  that  they  are  especially  adapted 
for  it  in  minor  details. 

The  chief  source  of  calcium  carbide  in  this  country 
is  the  electric  furnace.  Cheap  electrical  energy  from 
hydro-electric  developments,  such  as  the  Niagara 
plants,  have  done  much  to  make  the  earth  yield  its 
elements.  Aluminum  is  very  prevalent  in  the  soil  of 
the  earth’s  surface,  because  its  oxide,  alumina,  is  a 
chief  constituent  of  ordinary  clay.  But  the  elements, 
aluminum  and  oxygen,  cling  tenaciously  to  each  other 
and  only  the  electric  furnace  with  its  excessively  high 
temperatures  has  been  able  to  separate  them  on  a  large 
commercial  scale.  Similarly,  calcium  is  found  in  va¬ 
rious  compounds  over  the  earth’s  surface.  Limestone 
abounds  widely,  hence  the  oxide  and  carbonate  of  lime 
are  wide-spread.  But  calcium  clings  tightly  to  the 
other  elements  of  its  compounds  and  it  has  taken  the 
electric  furnace  to  bring  it  to  submission.  The  cheap¬ 
ness  of  calcium  carbide  is  due  to  the  development  of 
cheap  electric  power.  It  is  said  that  calcium  carbide 
was  discovered  as  a  by-product  of  the  electric  furnace 
by  accidentally  throwing  water  upon  the  waste  ma¬ 
terials  of  a  furnace  process.  The  discovery  of  a  com¬ 
mercial  scale  of  manufacture  of  calcium  carbide  has 


MODERN  GAS-LIGHTING 


109 


been  a  boon  to  isolated  lighting.  Electric  lighting  has 
usurped  its  place  on  the  automobile  and  is  making  in¬ 
roads  in  country-home  lighting.  Doubtless,  acetylene 
will  continue  to  serve  for  many  years,  but  its  future 
does  not  appear  as  bright  as  it  did  many  years  ago. 

The  Pintsch  gas,  used  to  some  extent  in  railroad  pas¬ 
senger-cars  in  this  country,  is  an  oil-gas  produced  by 
the  destructive  distillation  of  petroleum  or  other  min¬ 
eral  oil  in  retorts  heated  externally.  The  product  con¬ 
sists  chiefly  of  methane  and  heavy  hydrocarbons  with 
a  small  amount  of  hydrogen.  In  the  early  days  of 
railways,  some  trains  were  not  run  after  dark  and 
those  which  were  operated  were  not  always  lighted. 
At  first  attempts  were  made  at  lighting  railway  cars 
with  compressed  coal-gas,  but  the  disadvantage  of  this 
was  the  large  tank  required.  Obviously,  a  gas  of 
higher  illuminating-value  per  volume  was  desired 
where  limited  storage  space  was  available,  and  Pintsch 
turned  his  attention  to  oil-gas.  Gas  suffers  in  illum¬ 
inating-value  upon  being  compressed,  but  oil-gas 
suffers  only  about  half  the  loss  that  coal-gas  does.  In 
about  1880  Pintsch  developed  a  method  of  welding 
cylinders  and  buoys  which  satisfied  lighthouse  authori¬ 
ties  and  he  was  enabled  to  furnish  these  filled  with 
compressed  gas.  Thus  the  buoy  was  its  own  gas-tank. 
He  devised  lanterns  which  would  remain  lighted  re¬ 
gardless  of  wind  and  waves  and  thus  gained  a  start 
with  his  compressed-gas  systems.  He  compressed  the 
gas  to  a  pressure  of  about  one  hundred  and  fifty 
pounds  per  square  inch  and  was  obliged  to  devise  a  re¬ 
ducer  which  would  deliver  the  gas  to  the  burner  at 
about  one  pound  per  square  inch.  This  regulator 


110 


ARTIFICIAL  LIGHT 


served  well  throughout  many  years  of  exacting  service. 
The  system  began  to  be  adopted  on  ships  and  railroads 
in  1880  and  for  many  years  it  has  served  well. 

Although  gas-lighting  has  affected  the  activities  of 
mankind  considerably  by  intensifying  commerce  and 
industry  and  by  advancing  social  progress,  the  illum- 
inants  which  eventually  took  the  lead  have  extended 
the  possibilities  and  influences  of  artificial  light.  In 
the  brief  span  of  a  century  civilized  man  is  almost  to¬ 
tally  independent  of  natural  light  in  those  fields  over 
which  he  has  control.  What  another  century  will  bring 
can  be  predicted  only  from  the  accomplishments  of  the 
past.  These  indicate  possibilities  beyond  the  powers 
of  imagination. 


IX 


THE  ELECTRIC  ARCS 

Early  in  1800  Volta  wrote  a  letter  to  the  President 
of  the  Royal  Society  of  London  announcing  the 
epochal  discovery  of  a  device  now  known  as  the  vol¬ 
taic  pile.  This  letter  was  published  in  the  Transac¬ 
tions  and  it  created  great  excitement  among  scientific 
men,  who  immediately  began  active  investigations  of 
certain  electrical  phenomena.  Volta  showed  that  all 
metals  could  be  arranged  in  a  series  so  that  each  one 
would  indicate  a  positive  electric  potential  when  in 
contact  with  any  metal  following  it  in  the  series.  He 
constructed  a  pile  of  metal  disks  consisting  of  zinc  and 
copper  alternated  and  separated  by  wet  cloths.  At 
first  he  believed  that  mere  contact  was  sufficient,  but 
when,  later,  it  was  shown  that  chemical  action  took 
place,  rapid  progress  was  made  in  the  construction  of 
voltaic  cells.  The  next  step  after  his  pile  was  con¬ 
structed  was  to  place  pairs  of  strips  of  copper  and  zinc 
in  cups  containing  water  or  dilute  acid.  Volta  re¬ 
ceived  many  honors  for  his  discovery,  which  contrib¬ 
uted  so  much  to  the  development  of  electrical  science 
and  art — among  them  a  call  to  Paris  by  Bonaparte  to 
exhibit  his  electrical  experiments,  and  to  receive  a 
medal  struck  in  his  honor. 

While  Volta  was  being  showered  with  honors,  various 

scientific  men  with  great  enthusiasm  were  entering  new 

in 


112 


ARTIFICIAL  LIGHT 


fields  of  research,  among  which  was  the  heating  value 
of  electric  current  and  particularly  of  electric  sparks 
made  by  breaking  a  circuit.  Late  in  1800  Sir  Hum¬ 
phrey  Davy  was  the  first  to  use  charcoal  for  the  spark¬ 
ing  points.  In  a  lecture  before  the  Royal  Society  in 
the  following  year  he  described  and  demonstrated  that 
the  “ spark”  passing  between  two  pieces  of  charcoal 
was  larger  and  more  brilliant  than  between  brass 
spheres.  Apparently,  he  was  producing  a  feeble  arc, 
rather  than  a  pure  spark.  In  the  years  which  imme¬ 
diately  followed  many  scientific  men  in  England, 
France,  and  Germany  were  publishing  the  results  of 
their  studies  of  electrical  phenomena  bordering  upon 
the  arc. 

By  subscription  among  the  members  of  the  Royal 
Society,  a  voltaic  battery  of  two  thousand  cells  was 
obtained  and  in  1808  Davy  exhibited  the  electric  arc 
on  a  large  scale.  It  is  difficult  to  judge  from  the  re¬ 
ports  of  these  early  investigations  who  was  the  first 
to  recognize  the  difference  between  the  spark  and 
the  arc.  Certainly  the  descriptions  indicate  that  the 
simple  spark  was  not  being  experimented  with,  but 
the  source  of  electric  current  available  at  that  time  was 
of  such  high  resistance  that  only  feeble  arcs  could  have 
been  produced.  In  1809  Davy  demonstrated  publicly 
an  arc  obtained  by  a  current  from  a  Volta  pile  of  one 
thousand  plates.  This  he  described  as  “a  most  bril¬ 
liant  flame,  of  from  half  an  inch  to  one  and  a  quarter 
inches  in  length.  ’  ’ 

In  the  library  of  the  Royal  Society,  Davy’s  notes 
made  during  the  years  of  1805  and  1812  are  available 
in  two  large  volumes.  These  were  arranged  and  paged 


THE  ELECTRIC  ARCS 


113 


by  Faraday,  who  was  destined  to  contribute  greatly 
to  the  future  development  of  the  science  and  art  of 
electricity.  In  one  of  these  volumes  is  found  an  ac¬ 
count  of  a  lecture-experiment  by  Davy  which  certainly 
is  a  description  of  the  electric  arc.  An  extract  of  this 
account  is  as  follows : 

The  spark  [presumably  the  arc],  the  light  of  which 
was  so  intense  as  to  resemble  that  of  the  sun,  .  .  . 
produced  a  discharge  through  heated  air  nearly  three 
inches  in  length,  and  of  a  dazzling  splendor.  Several 
bodies  which  had  not  been  fused  before  were  fused  by 
this  flame  .  .  .  Charcoal  was  made  to  evaporate,  and 
plumbago  appeared  to  fuse  in  vacuo.  Charcoal  was 
ignited  to  intense  whiteness  by  it  in  oxymuriatic  acid, 
and  volatilized  by  it,  but  without  being  decomposed. 

From  a  consideration  of  his  source  of  electricity,  a 
voltaic  pile  of  two  thousand  plates,  it  is  certain  that 
this  could  not  have  been  an  electric  spark.  Later  in 
his  notes  Davy  continued: 

.  .  .  the  charcoal  became  ignited  to  whitness,  and  by 
withdrawing  the  points  from  each  other,  a  constant  dis¬ 
charge  took  place  through  the  heated  air,  in  a  space 
at  least  equal  to  four  inches,  producing  a  most  bril¬ 
liant  ascending  arch  of  light,  broad  and  conical  in  form 
in  the  middle. 

This  is  surely  a  description  of  the  electric  arc.  Ap¬ 
parently  the  electrodes  were  in  a  horizontal  position 
and  the  arc  therefore  was  horizontal.  Owing  to  the 
rise  of  the  heated  air,  the  arc  tended  to  rise  in  the  form 
of  an  arch.  From  this  appearance  the  term  “arc” 
evolved  and  Davy  himself  in  1820  definitely  named  the 


114 


ARTIFICIAL  LIGHT 


electric  flame,  the  “arc.”  This  name  was  continued 
in  use  even  after  the  two  carbons  were  arranged  in  a 
vertical  co-axial  position  and  the  arc  no  more 
“arched.”  An  interesting  scientific  event  of  1820  was 
the  discovery  by  Arago  and  by  Davy  independently 
that  the  arc  could  be  deflected  by  a  magnet  and  that 
it  was  similar  to  a  wire  carrying  current  in  that  there 
was  a  magnetic  field  around  it.  This  has  been  taken 
advantage  of  in  certain  modern  arc-lamps  in  which  in¬ 
clined  carbons  are  used.  In  these  arcs  a  magnet  keeps 
the  arc  in  place,  for  without  the  magnet  the  arc  would 
tend  to  climb  up  the  carbons  and  go  out. 

In  1838  Gassiot  made  the  discovery  that  the  tempera¬ 
ture  of  the  positive  electrode  of  an  electric  arc  is  much 
greater  than  that  of  the  negative  electrode.  This  is 
explained  in  electronic  theory  by  the  bombardment  of 
the  positive  electrode  by  negative  electrons  or  cor¬ 
puscles  of  electricity.  This  temperature-difference 
was  later  taken  into  account  in  designing  direct-current 
arc-lamps,  for  inasmuch  as  most  of  the  light  from  an 
ordinary  arc  is  emitted  by  the  end  of  the  positive  elec¬ 
trode,  this  was  placed  above  the  negative  electrode. 
In  this  manner  most  of  the  light  from  the  arc  is  di¬ 
rected  downward  where  desired.  In  the  few  instances 
in  modern  times  where  the  ordinary  direct-current  arc 
has  been  used  for  indirect  lighting,  in  which  case  the  arc 
is  above  an  inverted  shade,  the  positive  carbon  is 
placed  below  the  negative  one.  Gassiot  first  proved 
that  the  positive  electrode  is  hotter  than  the  negative 
one  by  striking  an  arc  between  the  ends  of  two  hori¬ 
zontal  wires  of  the  same  substance  and  diameter. 
After  the  arc  operated  for  some  time,  the  positive  wire 


THE  ELECTRIC  ARCS 


115 


was  melted  for  such  a  distance  that  it  bent  downward, 
but  the  negative  remained  quite  straight. 

Charcoal  was  used  for  the  electrodes  in  all  the  early 
experiments,  but  owing  to  the  intense  heat  of  the  arc, 
it  burned  away  rapidly.  A  progressive  step  was  made 
in  1843  when  electrodes  were  first  made  by  Foucault 
from  the  carbon  deposited  in  retorts  in  which  coal  was 
distilled  in  the  production  of  coal-gas.  However, 
charcoal,  owing  to  its  soft  porous  character,  gives  a 
longer  arc  and  a  larger  flame.  In  1877  the  “ cored” 
carbons  were  introduced.  These  consist  of  hard 
molded  carbon  rods  in  which  there  is  a  core  of  soft 
carbon.  In  these  are  combined  the  advantages  of  char¬ 
coal  and  hard  carbon  and  the  core  in  burning  away 
more  rapidly  has  a  tendency  to  hold  the  arc  in  the 
center.  Modern  carbons  for  ordinary  arc-lamps  are 
generally  made  of  a  mixture  of  retort-carbon,  soot,  and 
coal-tar.  This  paste  is  forced  through  dies  and  the 
carbons  are  baked  at  a  fairly  high  temperature.  A 
variation  in  the  hardness  of  the  carbons  may  be  ob¬ 
tained  as  the  requirements  demand  by  varying  the 
proportions  of  soot  and  retort-carbon.  Cored  car¬ 
bons  are  made  by  inserting  a  small  rod  in  the  center  of 
the  die  and  the  carbons  are  formed  with  a  hollow  core. 
This  may  be  filled  with  a  softer  carbon. 

If  two  carbons  connected  to  a  source  of  electric  cur¬ 
rent  are  brought  together,  the  circuit  is  completed  and 
a  current  flows.  If  the  two  carbons  are  now  slightly 
separated,  an  arc  will  be  formed.  As  the  arc  burns  the 
carbons  waste  away  and  in  the  case  of  direct  current, 
the  positive  decreases  in  length  more  rapidly  than  the 
negative  one.  This  is  due  largely  to  the  extremely 


116 


ARTIFICIAL  LIGHT 


high  temperature  of  the  positive  tip,  where  the  carbon 
fairly  boils.  A  crater  is  formed  at  the  positive  tip 
and  this  is  always  characteristic  of  the  positive  car¬ 
bon  of  the  ordinary  arc,  although  it  becomes  more  shal¬ 
low  as  the  arc-length  is  increased.  The  negative  tip 
has  a  bright  spot  to  which  one  end  of  the  arc  is  at¬ 
tached.  By  wasting  away,  the  length  of  the  arc  in¬ 
creases  and  likewise  its  resistance,  until  finally  insuffi¬ 
cient  current  will  pass  to  maintain  the  arc.  It  then 
goes  out  and  to  start  it  the  carbons  must  be  brought 
together  and  separated.  The  mechanisms  of  modern 
arc-lamps  perform  these  functions  automatically  by  the 
ingenious  use  of  electromagnets. 

The  interior  of  the  arc  is  of  a  violet  color  and  the 
exterior  is  a  greenish  yellow.  The  white-hot  spot  on 
the  negative  tip  is  generally  surrounded  by  a  fringe  of 
agitated  globules  which  consist  of  tar  and  other  in¬ 
gredients  of  carbons.  Often  material  is  deposited  from 
the  positive  crater  upon  the  negative  tip  and  these  ac¬ 
cretions  may  build  up  a  rounded  tip.  This  deposit 
sometimes  interferes  with  the  proper  formation  of  the 
arc  and  also  with  the  light  from  the  arc.  It  is  often 
responsible  for  the  hissing  noise,  although  this  hissing 
occurs  with  any  length  of  arc  when  the  current  is  suffi¬ 
ciently  increased.  The  hissing  seems  to  be  due  to  the 
crater  enlarging  under  excessive  current  until  it  passes 
the  confines  of  the  cross-section  of  the  carbon.  It  thus 
tends  to  run  up  the  side,  where  it  comes  in  contact  with 
oxygen  of  the  air.  In  this  manner  the  carbon  is  di¬ 
rectly  burned  instead  of  being  vaporized,  as  it  is  when 
the  hot  crater  is  small  and  is  protected  from  the  air  by 
the  arc  itself.  The  temperature  of  the  positive  crater 


THE  ELECTRIC  ARCS 


117 


is  in  the  neighborhood  of  6000°  to  7000° F.  The 
brightness  of  the  arc  under  pressure  is  the  greatest 
produced  by  artificial  means  and  is  very  intense.  By 
putting  the  arc  under  high  pressure,  the  brightness  of 
the  sun  may  be  attained.  The  temperature  of  the  hot¬ 
test  spot  on  the  negative  tip  is  about  a  thousand  de¬ 
grees  below  that  of  the  positive. 

No  great  demand  arose  for  arc-lamps  until  the  de¬ 
velopment  of  the  Gramme  dynamo  in  1870,  which  pro¬ 
vided  a  practicable  source  of  electric  current.  In  1876 
Jablochkov  invented  his  famous  “ electric  candle’ ’  con¬ 
sisting  of  two  rods  of  carbon  placed  side  by  side  but 
separated  by  insulating  material.  In  this  country 
Brush  was  the  pioneer  in  the  development  of  open  arc- 
lamps.  In  1877  he  invented  an  arc-lamp  and  an  effi¬ 
cient  form  of  dynamo  to  supply  the  electrical  energy. 
The  first  arc-lamps  were  ordinary  direct-current  open 
arcs  and  the  carbons  were  made  from  high-grade  coke, 
lampblack,  and  syrup.  The  upper  positive  carbon  in 
these  lamps  is  consumed  at  a  rate  of  one  to  two  inches 
per  hour.  Inasmuch  as  about  85  per  cent,  of  the  total 
light  is  emitted  by  the  upper  (positive)  carbon  and 
most  of  this  from  the  crater,  the  lower  carbon  is  made 
as  small  as  possible  in  order  not  to  obstruct  any  more 
light  than  necessary.  The  positive  carbon  of  the  open 
arc  is  often  cored  and  the  negative  is  a  smaller  one  of 
solid  carbon.  This  combination  operates  quite  satis¬ 
factorily,  but  sometimes  solid  carbons  are  used  out¬ 
doors.  The  voltage  across  the  arc  is  about  50  volts. 

In  1846  Staite  discovered  that  the  carbons  of  an  arc 
enclosed  in  a  glass  vessel  into  which  the  air  was  not 
freely  admitted  were  consumed  less  rapidly  than  when 


118 


ARTIFICIAL  LIGHT 


the  arc  operated  in  the  open  air.  After  the  appear¬ 
ance  of  the  dynamo,  when  increased  attention  was 
given  to  the  development  of  arc-lamps,  this  principle 
of  enclosing  the  arcs  was  again  considered.  The  early 
attempts  in  about  1880  were  unsuccessful  because  low 
voltages  were  used  and  it  was  not  until  the  discovery 
was  made  that  the  negative  tip  builds  up  considerably 
for  voltages  under  65  volts,  that  higher  voltages  were 
employed.  In  1893  marked  improvements  were  con¬ 
summated  and  Jandus  brought  out  a  successful  en¬ 
closed  arc  operating  at  80  volts.  Marks  contributed 
largely  to  the  success  of  the  enclosed  arc  by  showing 
that  a  small  current  and  a  high  voltage  of  80  to  85 
volts  were  the  requisites  for  a  satisfactory  enclosed 
arc. 

The  principle  of  the  enclosed  arc  is  simple.  A 
closely  fitting  glass  globe  surrounds  the  arc,  the  fit  be¬ 
ing  as  close  as  the  feeding  of  the  carbons  will  permit. 
When  the  arc  is  struck  the  oxygen  is  rapidly  consumed 
and  the  heated  gases  and  the  enclosure  check  the  sup¬ 
ply  of  fresh  air.  The  result  is  that  the  carbons  are 
consumed  about  one  tenth  as  rapidly  as  in  the  open 
arc.  There  is  no  crater  formed  on  the  positive  tip  and 
the  arc  wanders  considerably.  The  efficiency  of  the  en¬ 
closed  arc  as  a  light-producer  is  lower  than  that  of  the 
open  arc,  but  it  found  favor  because  of  its  slow  rate 
of  consumption  of  the  carbons  and  consequent  de¬ 
creased  attention  necessary.  This  arc  operates  a  hun¬ 
dred  hours  or  more  without  trimming,  and  will  there¬ 
fore  operate  a  week  or  more  in  street-lighting  without 
attention.  When  it  is  considered  that  open  arcs  for  all- 


THE  ELECTRIC  ARCS 


119 


night  burning  were  supplied  with  two  pairs  of  car¬ 
bons,  the  second  set  going  into  use  automatically  when 
the  first  were  consumed,  the  value  of  the  enclosed  arc 
is  apparent.  However,  the  open  arc  has  served  well 
and  has  given  way  to  greater  improvements.  It  is 
rapidly  disappearing  from  use. 

The  alternating-current  arc-lamp  was  developed  after 
the  appearance  of  the  direct-current  open-arc  and  has 
been  widely  used.  It  has  no  positive  or  negative  car¬ 
bons,  for  the  alternating  current  is  reversing  in  direc¬ 
tion  usually  at  the  rate  of  120  times  per  second;  that 
is,  it  passes  through  60  complete  cycles  during  each 
second.  No  marked  craters  form  on  the  tips  and  the 
two  carbons  are  consumed  at  about  the  same  rate. 
The  average  temperature  of  the  carbon  tips  is  lower 
than  that  of  the  positive  tip  of  a  direct-current  arc, 
with  the  result  that  the  luminous  efficiency  is  lower. 
These  arcs  have  been  made  of  both  the  open  and  en¬ 
closed  type.  They  are  characterized  by  a  humming 
noise  due  to  the  effect  of  alternating  current  upon  the 
mechanism  and  also  upon  the  air  near  the  arc.  This 
humming  sound  is  quite  different  from  the  occasional 
hissing  of  a  direct-current  arc.  When  soft  carbons  are 
used,  the  arc  is  larger  and  apparently  this  mass  of 
vapor  reduces  the  humming  considerably.  The  hum¬ 
ming  is  not  very  apparent  for  the  enclosed  alternating- 
current  arc.  The  alternating  arc  can  easily  be  de¬ 
tected  by  closely  observing  moving  objects.  If  a  pen¬ 
cil  or  coin  be  moved  rapidly,  a  number  of  images  ap¬ 
pear  which  are  due  to  the  pulsating  character  of  the 
light.  At  each  reversal  of  the  current,  the  current 


120 


ARTIFICIAL  LIGHT 


reaches  zero  value  and  the  arc  is  virtually  extinguished. 
Therefore,  there  is  a  maximum  brightness  midway  be¬ 
tween  the  reversals. 

Various  types  of  all  these  arcs  have  been  developed 
to  meet  the  different  requirements  of  ordinary  light¬ 
ing  and  to  adapt  this  method  of  light-production  to  the 
needs  of  projection,  stage-equipment,  lighthouses, 
search-lights,  and  other  applications. 

Up  to  this  point  the  ordinary  carbon  arc  has  been 
considered  and  it  has  been  seen  that  most  of  the  light 
is  emitted  by  the  glowing  end  of  the  positive  carbon. 
In  fact,  the  light  from  the  arc  itself  is  negligible.  A 
logical  step  in  the  development  of  the  arc-lamp  was  to 
introduce  salts  in  order  to  obtain  a  luminous  flame. 
This  possibility  as  applied  to  ordinary  gas-flames  had 
been  known  for  years  and  it  is  surprising  that  it  had 
not  been  early  applied  to  carbons.  Apparently  Bremer 
in  1898  was  the  first  to  introduce  fluorides  of  calcium, 
barium,  and  strontium.  The  salts  deflagrate  and  a 
luminous  flame  envelops  the  ordinary  feeble  arc-flame. 
From  these  arcs  most  of  the  light  is  emitted  by  the  arc 
itself,  hence  the  name  “flame-arcs.” 

By  the  introduction  of  metallic  salts  into  the  car¬ 
bons  the  possibilities  of  the  arc-lamp  were  greatly  ex¬ 
tended.  The  luminous  output  of  such  lamps  is  much 
greater  than  that  of  an  ordinary  carbon  arc  using  the 
same  amount  of  electrical  energy.  Furthermore,  the 
color  or  spectral  character  of  the  light  may  be  varied 
through  a  wide  range  by  the  use  of  various  salts.  For 
example,  if  carbons  are  impregnated  with  calcium 
fluoride,  the  arc-flame  when  examined  by  means  of  a 
spectroscope  will  be  seen  to  contain  the  characteristic 


THE  ELECTRIC  ARCS 


121 


spectrum  of  calcium,  namely,  some  green,  orange,  and 
red  rays.  These  combine  to  give  to  this  arc  a  very 
yellow  color.  As  explained  in  a  previous  chapter,  the 
salts  for  this  purpose  may  be  wisely  chosen  from  a 
knowledge  of  their  fundamental  or  characteristic  flame- 
spectra. 

These  lamps  have  been  developed  to  meet  a  variety 
of  needs  and  their  luminous  efficiencies  range  from  20 
to  40  lumens  per  watt,  being  several  times  that  of  the 
ordinary  carbon  open-arc.  The  red  flame-arc  owes  its 
color  chiefly  to  strontium,  whose  characteristic  visible 
spectrum  consists  chiefly  of  red  and  yellow  rays.  Bar¬ 
ium  gives  to  the  arc  a  fairly  white  color.  The  yellow 
and  so-called  white  flame-arcs  have  been  most  com¬ 
monly  used.  Flame-arcs  have  been  produced  which 
are  close  to  daylight  in  color,  and  powerful  blue-white 
flame-arcs  have  satisfied  the  needs  of  various  chemical 
industries  and  photographic  processes.  These  arcs  are 
generally  operated  in  a  space  where  the  air-supply  is 
restricted  similar  to  the  enclosed-arc  principle.  In¬ 
asmuch  as  poisonous  fumes  are  emitted  in  large  quan¬ 
tities  from  some  flame-arcs,  they  are  not  used  indoors 
without  rather  generous  ventilation.  In  fact,  the 
flame-arcs  are  such  powerful  light-sources  that  they 
are  almost  entirely  used  outdoors  or  in  very  large 
interiors  especially  of  the  type  of  open  factory  build¬ 
ings.  They  are  made  for  both  direct  and  alternating 
current  and  the  mechanisms  have  been  of  several  types. 
The  electrodes  are  consumed  rather  rapidly  so  they 
are  made  as  long  as  possible.  In  one  type  of  arc,  the 
carbons  are  both  fed  downward,  their  lower  ends  form¬ 
ing  a  narrow  V  with  the  arc-flame  between  their  tips. 


122 


ARTIFICIAL  LIGHT 


Under  these  conditions  the  arc  tends  to  travel  ver¬ 
tically  and  finally  to  “ stretch’ ’  itself  to  extinction. 
However,  the  arc  is  kept  in  place  by  means  of  a  magnet 
above  it  which  repels  the  arc  and  holds  it  at  the  ends  of 
the  carbons. 

The  chief  objection  to  the  early  flame-arcs  was  the 
necessity  for  frequent  renewal  of  the  carbons.  This 
was  overcome  to  a  large  extent  in  the  Jandus  regener¬ 
ative  lamp  in  which  the  arc  operates  in  a  glass  enclos¬ 
ure  surrounded  by  an  opal  globe.  However,  in  addi¬ 
tion  to  the  inner  glass  enclosure,  two  cooling  chambers 
of  metal  are  attached  to  it.  Air  enters  at  the  bottom 
and  the  fumes  from  the  arc  pass  upward  and  into  the 
cooling  chambers,  where  the  solid  products  are  de¬ 
posited.  The  air  on  returning  to  the  bottom  is  thus 
relieved  of  these  solids  and  the  inner  glass  enclosure 
remains  fairly  clean.  The  lower  carbon  is  impregnated 
with  salts  for  producing  the  luminous  flame  and  the 
upper  carbon  is  cored.  The  life  of  the  electrodes  is 
about  seventy-five  hours. 

The  next  step  was  the  introduction  of  the  so-called 
“luminous-arc”  which  is  a  4 4 flame-arc’ ,  with  entirely 
different  electrodes.  The  lower  (negative)  electrode 
consists  of  an  iron  tube  packed  chiefly  with  magnetite 
(an  iron  oxide)  and  titanium  oxide  in  the  approximate 
proportions  of  three  to  one  respectively.  The  mag¬ 
netite  is  a  conductor  of  electricity  which  is  easily  va¬ 
porized.  The  arc-flame  is  large  and  the  titanium  gives 
it  a  high  brilliancy.  The  positive  electrode,  usually 
the  upper  one,  is  a  short,  thick,  solid  cylinder  of  cop¬ 
per,  which  is  consumed  very  slowly.  This  lamp,  known 


THE  ELECTRIC  ARCS 


123 


as  the  magnetite-arc,  has  a  luminous  efficiency  of  about 
20  lumens  per  watt  with  a  clear  glass  globe. 

The  mechanisms  which  strike  the  arc  and  feed  the 
carbons  are  ingenious  devices  of  many  designs  depend¬ 
ing  upon  the  kind  of  arc  and  upon  the  character  of 
the  electric  circuit  to  which  it  is  connected.  Late  de¬ 
velopments  in  electric  incandescent  filament  lamps 
have  usurped  some  of  the  fields  in  which  the  arc-lamp 
reigned  supreme  for  years  and  its  future  does  not  ap¬ 
pear  as  bright  now  as  it  did  ten  years  ago.  High-in¬ 
tensity  arcs  have  been  devised  with  small  carbons  for 
special  purposes  and  considered  as  a  whole  a  great 
amount  of  ingenuity  has  been  expended  in  the  develop¬ 
ment  of  arc-lamps.  There  will  be  a  continued  demand 
for  arc-lamps,  for  scientific  developments  are  opening 
new  fields  for  them.  Their  value  in  photo-engraving, 
in  the  moving-picture  production  studios,  in  moving- 
picture  projection,  and  in  certain  aspects  of  stage¬ 
lighting  is  firmly  established,  and  it  appears  that  they 
will  find  application  in  certain  chemical  industries  be¬ 
cause  the  arc  is  a  powerful  source  of  radiant  energy 
which  is  very  active  in  its  effects  upon  chemical  reac¬ 
tions. 

The  luminous  efficiencies  of  arc-lamps  depend  upon 
so  many  conditions  that  it  is  difficult  to  present  a  con¬ 
cise  comparison;  however,  the  following  may  suffice 
to  show  the  ranges  of  luminous  output  per  watt  under 
actual  conditions  of  usage.  These  efficiencies,  of 
course,  are  less  than  the  efficiencies  of  the  arc  alone, 
because  the  losses  in  the  mechanism,  globes,  etc.,  are 
included. 


124 


ARTIFICIAL  LIGHT 


Lumens  per  watt 


Open  carbon  arc  .  4  to  8 

Enclosed  carbon  arc  .  3  to  7 

Enclosed  flame-arc  (yellow  or  white)  . .  15  to  25 
Luminous  arc .  10  to  25 


Another  lamp  differing  widely  in  appearance  from 
the  preceding  arcs  may  be  described  here  because  it 
is  known  as  the  mercury-arc.  In  this  lamp  mercury 
is  confined  in  a  transparent  tube  and  an  arc  is  started 
by  making  and  breaking  a  mercury  connection  between 
the  two  electrodes.  The  arc  may  be  maintained  of  a 
length  of  several  feet.  Perhaps  the  first  mercury-arc 
was  produced  in  1860  by  Way,  who  permitted  a  fine 
jet  of  mercury  to  fall  from  a  reservoir  into  a  vessel, 
the  reservoir  and  receiver  being  connected  to  the  poles 
of  a  battery.  The  electric  current  scattered  the  jet 
and  between  the  drops  arcs  were  formed.  He  ex¬ 
hibited  this  novel  light-source  on  the  mast  of  a  yacht 
and  it  received  great  attention.  Later,  various  inves¬ 
tigators  experimented  on  the  production  of  a  mercury- 
arc  and  the  first  successful  ones  were  made  in  the  form 
of  an  inverted  U-tube  with  the  ends  filled  with  mer¬ 
cury  and  the  remainder  of  the  tube  exhausted. 

Cooper  Hewitt  was  a  successful  pioneer  in  the  pro¬ 
duction  of  practicable  mercury-arcs.  He  made  them 
chiefly  in  the  form  of  straight  tubes  of  glass  up  to 
several  feet  in  length,  with  enlarged  ends  to  facilitate 
cooling.  The  tubes  are  inclined  so  that  the  mercury 
vapor  which  condenses  will  run  back  into  the  enlarged 
end,  where  a  pool  of  mercury  forms  the  negative  elec¬ 
trode.  The  arc  may  be  started  by  tilting  the  tube  so 
that  a  mercury  thread  runs  down  the  side  and  con- 


THE  ELECTRIC  ARCS 


125 


nects  with  the  positive  electrode  of  iron.  The  heat 
of  the  arc  volatilizes  the  mercury  so  that  an  arc  of  con¬ 
siderable  length  is  maintained.  The  tilting  is  done  by 
electromagnets.  Starting  has  also  been  accomplished 
by  means  of  a  heating  coil  and  also  by  an  electric 
spark.  The  lamps  are  stabilized  by  resistance  and  in¬ 
ductance  coils. 

One  of  the  defects  of  the  light  emitted  by  the  incan¬ 
descent  vapor  of  mercury  is  its  paucity  of  spectral 
colors.  Its  visible  spectrum  consists  chiefly  of  violet, 
blue,  green,  and  yellow  rays.  It  emits  virtually  no 
red  rays,  and,  therefore,  red  objects  appear  devoid  of 
red.  The  human  face  appears  ghastly  under  this  light 
and  it  distorts  colors  in  general.  However,  it  pos¬ 
sesses  the  advantages  of  high  efficiency,  of  reasonably 
low  brightness,  of  high  actinic  value,  and  of  revealing 
detail  clearly.  Various  attempts  have  been  made  to 
improve  the  color  of  the  light  by  adding  red  rays. 
Reflectors  of  a  fluorescent  red  dye  have  been  used  with 
some  success,  but  such  a  method  reduces  the  luminous 
efficiency  of  the  lamp  considerably.  The  dye  fluoresces 
red  under  the  illumination  of  ultra-violet,  violet,  and 
blue  rays ;  that  is,  it  has  the  property  of  converting 
radiation  of  these  wave-lengths  into  radiant  energy  of 
longer  wave-lengths.  By  the  use  of  electric  incandes¬ 
cent  filament  lamps  in  conjunction  with  mercury-arcs, 
a  fairly  satisfactory  light  is  obtained.  Many  experi¬ 
ments  have  been  made  by  adding  other  substances  to 
the  mercury,  such  as  zinc,  with  the  hope  that  the  spec¬ 
trum  of  the  other  substance  would  compensate  the 
defects  in  the  mercury  spectrum.  However  no  suc¬ 
cess  has  been  reached  in  this  direction. 


126 


ARTIFICIAL  LIGHT 


By  the  use  of  a  quartz  tube  which  can  withstand  a 
much  higher  temperature  than  glass,  the  current  den¬ 
sity  can  be  greatly  increased.  Thus  a  small  quartz 
tube  of  incandescent  mercury  vapor  will  emit  as  much 
light  as  a  long  glass  tube.  The  quartz  mercury-arc 
produces  a  light  which  is  almost  white,  but  the  actual 
spectrum  is  very  different  from  that  of  white  sunlight. 
Although  some  red  rays  are  emitted  by  the  quartz  arc, 
its  spectrum  is  essentially  the  same  as  that  of  the  glass- 
tube  arc.  Quartz  transmits  ultra-violet  radiation, 
which  is  harmful  to  the  eyes,  and  inasmuch  as  the 
mercury  vapor  emits  such  rays,  a  glass  globe  should 
be  used  to  enclose  the  quartz  tube  when  the  lamp  is 
used  for  ordinary  lighting  purposes. 

It  is  fortunate  that  such  radically  different  kinds  of 
light-sources  are  available,  for  in  the  complex  activi¬ 
ties  of  the  present  time  all  are  in  demand.  The  quartz 
mercury-arc  finds  many  isolated  uses,  owing  to  its 
wealth  of  ultra-violet  radiation.  It  is  valuable  as  a 
source  of  ultra-violet  for  exciting  phosphorescence,  for 
examining  the  transmission  of  glasses  for  this  radia¬ 
tion,  for  sterilizing  water,  for  m'edical  purposes,  and 
for  photography. 


X 


THE  ELECTRIC  INCANDESCENT  FILAMENT 

LAMPS 

Prior  to  1800  electricity  was  chiefly  a  plaything  for 
men  of  scientific  tendencies  and  it  was  not  until  Volta 
invented  the  electric  pile  or  battery  that  certain  scien¬ 
tific  men  gave  their  entire  attention  to  the  study  of 
electricity.  Volta  was  not  merely  an  inventor,  for  he 
was  one  of  the  greatest  scientists  of  his  period,  en¬ 
dowed  with  an  imagination  which  marked  him  as  a 
genius  in  creative  work.  By  contributing  the  electric 
battery,  he  added  the  greatest  impetus  to  research  in 
electrical  science  that  it  has  ever  received.  As  has  al¬ 
ready  been  shown,  there  began  a  period  of  enthusiastic 
research  in  the  general  field  of  heating  effects  of  elec¬ 
tric  current.  The  electric  arc  was  born  in  the  cradle  of 
this  enthusiasm,  and  in  the  heating  of  metals  by  elec¬ 
tricity  the  future  incandescent  lamp  had  its  beginning. 

Between  the  years  1841  and  1848  several  inventors 
attempted  to  make  light-sources  by  heating  metals. 
These  crude  lamps  were  operated  by  means  of  Grove 
and  Bunsen  electric  cells,  but  no  practicable  incandes¬ 
cent  filament  lamps  were  brought  out  until  the  devel¬ 
opment  of  the  electric  dynamo  supplied  an  adequate 
source  of  electric  current.  As  electrical  science  prog¬ 
ressed  through  the  continued  efforts  of  scientific  men, 

it  finally  became  evident  that  an  adequate  supply  of 

127 


128 


ARTIFICIAL  LIGHT 


electric  current  could  be  obtained  by  mechanical  means ; 
that  is,  by  rotating  conductors  in  such  a  manner  that 
current  would  be  generated  within  them  as  they  cut 
through  a  magnetic  field.  Even  the  pioneer  inventors 
of  electric  lamps  made  great  contributions  to  electrical 
practice  by  developing  the  dynamo.  Brush  developed 
a  satisfactory  dynamo  coincidental  with  his  invention 
of  the  arc-lamp,  and  in  a  similar  manner,  Edison  made 
a  great  contribution  to  electrical  practice  in  devising 
means  of  generating  and  distributing  electricity  for 
the  purpose  of  serving  his  filament  lamp. 

Edison  in  1878  attacked  the  problem  of  producing 
light  from  a  wire  or  filament  heated  electrically.  He 
used  platinum  wire  in  his  first  experiments,  but  its 
volatility  and  low  melting-point  (3200°F.)  limited  the 
success  of  the  lamps.  Carbon  with  its  extremely  high 
melting-point  had  long  attracted  attention  and  in  1879 
Edison  produced  a  carbon  filament  by  carbonizing  a 
strip  of  paper.  He  sealed  this  in  a  vessel  of  glass 
from  which  the  air  was  exhausted  and  the  electric  cur¬ 
rent  was  led  to  the  filament  through  platinum  wires 
sealed  in  the  glass.  Platinum  was  used  because  its  ex¬ 
pansion  and  contraction  is  about  the  same  as  glass. 
Incidentally,  many  improvements  were  made  in  incan¬ 
descent  lamps  and  thirty  years  passed  before  a  ma¬ 
terial  was  found  to  replace  the  platinum  leading-in 
wires.  The  cost  of  platinum  steadily  increased  and 
finally  in  the  present  century  a  substitute  was  made  by 
the  use  of  two  metals  whose  combined  expansion  was 
the  same  as  that  of  platinum  or  glass.  In  1879  and 
1880  Edison  had  succeeded  in  overcoming  the  many 


DIRECT  CURRENT  ARC  FLAME  ARC 

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INCANDESCENT  FILAMENT  LAMPS  129 


difficulties  sufficiently  to  give  to  the  world  a  prac¬ 
ticable  incandescent  filament  lamp.  About  this  time 
Swan  and  Stearn  in  England  had  also  produced  a  suc¬ 
cessful  lamp. 

In  Edison’s  early  experiments  with  filaments  he 
used  platinum  wire  coated  with  carbon  but  without 
much  success.  He  also  made  thin  rods  of  a  mixture  of 
finely  divided  metals  such  as  platinum  and  iridium 
mixed  with  such  oxides  as  magnesia,  zireonia,  and 
lime.  He  even  coiled  platinum  wire  around  a  piece 
of  one  of  these  oxides,  with  the  aim  of  obtaining  light 
from  the  wire  and  from  the  heated  oxide.  However, 
these  experiments  served  little  purpose  besides  indi¬ 
cating  that  the  filament  was  best  if  it  consisted  solely 
of  carbon  and  that  it  should  be  contained  in  an  evac¬ 
uated  vessel. 

One  of  the  chief  difficulties  was  to  make  the  carbon 
filaments.  Some  of  the  pioneers,  such  as  Sawyer  and 
Mann,  attempted  to  cut  these  from  a  piece  of  carbon. 
However,  Edison  and  also  Swan  turned  their  attention 
to  forming  them  by  carbonizing  a  fiber  of  organic  mat¬ 
ter.  Filaments  cut  from  paper  and  threads  of  cotton 
and  silk  were  carbonized  for  this  purpose.  Edison 
scoured  the  earth  for  better  materials.  He  tried  a 
fibrous  grass  from  South  America  and  various  kinds 
of  bamboo  from  other  parts  of  the  world.  Thin  fila¬ 
ments  of  split  bamboo  eventually  proved  the  best  ma¬ 
terial  up  to  that  time.  He  made  many  lamps  contain¬ 
ing  filaments  of  this  material,  and  even  until  1910  bam¬ 
boo  was  used  to  some  extent  in  certain  lamps. 

Of  these  early  days,  Edison  said : 


130 


ARTIFICIAL  LIGHT 


It  occurred  to  me  that  perhaps  a  filament  of  carbon 
could  be  made  to  stand  in  sealed  glass  vessels,  or  bulbs, 
which  we  were  using,  exhausted  to  a  high  vacuum. 
Separate  lamps  were  made  in  this  way  independent  of 
the  air-pump,  and,  in  October,  1879,  we  made  lamps  of 
paper  carbon,  and  with  carbons  of  common  sewing 
thread,  placed  in  a  receiver  or  bulb  made  entirely  of 
glass,  with  the  leading-in  wires  sealed  in  by  fusion. 
The  whole  thing  was  exhausted  by  the  Sprengel  pump 
to  nearly  one-millionth  of  an  atmosphere.  The  fila¬ 
ments  of  carbon,  although  naturally  quite  fragile  ow¬ 
ing  to  their  length  and  small  mass,  had  a  smaller  rad¬ 
iating  surface  and  higher  resistance  than  we  had  dared 
hope.  We  had  virtually  reached  the  position  and  con¬ 
dition  where  the  carbons  were  stable.  In  other  words, 
the  incandescent  lamp  as  we  still  know  it  to-day 
[1904],  in  essentially  all  its  particulars  unchanged,  had 
been  born. 

After  Edison’s  later  success  with  bamboo,  Swan  in¬ 
vented  a  process  of  squirting  filaments  of  nitrocellulose 
into  a  coagulating  liquid,  after  which  they  are  carbon¬ 
ized.  Very  fine  uniform  filaments  can  be  made  by  this 
process  and  although  improvements  have  been  made 
from  time  to  time,  this  method  has  been  employed  ever 
since  its  invention.  In  these  later  years  cotton  is  dis¬ 
solved  in  a  suitable  solvent  such  as  a  solution  of  zinc 
chloride  and  this  material  is  forced  through  a  small 
diamond  die.  This  thread  when  hardened  appears 
similar  to  cat-gut.  It  is  cut  into  proper  lengths  and 
bent  upon  a  form.  It  is  then  immersed  in  plumbago 
and  heated  to  a  high  temperature  in  order  to  destroy 
the  organic  matter.  A  carbon  filament  is  the  result. 
From  this  point  to  the  finished  lamp  many  operations 
are  performed,  but  a  discussion  of  these  would  lead 


INCANDESCENT  FILAMENT  LAMPS  131 


far  afield.  The  production  of  a  high  vacuum  is  one 
of  the  most  important  processes  and  manufacturers 
of  incandescent  lamps  have  mastered  the  art  perhaps 
more  thoroughly  than  any  other  manufacturers.  At 
least,  their  experience  in  this  field  made  it  possible 
for  them  to  produce  quickly  and  on  a  large  scale  such 
devices  as  X-ray  tubes  during  the  recent  war. 

During  the  early  years  of  incandescent  lamps,  im¬ 
provements  were  made  from  time  to  time  which  in¬ 
creased  the  life  and  the  luminous  efficiency  of  the  car¬ 
bon  filaments,  but  it  was  not  until  1906  that  any  radi¬ 
cal  improvement  was  achieved.  In  that  year  in  this 
country  a  process  was  devised  whereby  the  carbon  fila¬ 
ment  was  made  more  compact.  In  fact,  from  its  ap¬ 
pearance  it  received  the  name  “ metallized  filament.” 
These  carbon  filaments  are  prepared  in  the  same  man¬ 
ner  as  the  earlier  ones  but  are  finally  “treated”  by 
heating  in  an  atmosphere  of  hydrocarbons  such  as  coal- 
gas.  The  filament  is  heated  by  electric  current  and  the 
heat  breaks  down  the  hydrocarbons,  with  the  result 
that  carbon  is  deposited  upon  the  filament.  This 
“treated”  filament  has  a  coating  of  hard  carbon  and  its 
electrical  resistance  is  greater  than  that  of  the  un¬ 
treated  filament. 

The  luminous  efficiency  of  a  carbon  filament  is  a  func¬ 
tion  of  its  temperature  and  it  increases  very  rapidly 
with  increasing  temperature.  For  this  reason  it  is  a 
constant  aim  to  reach  high  filament  temperatures.  Of 
all  the  materials  used  in  filaments  up  to  the  present 
time,  carbon  possesses  the  highest  melting-point  (per¬ 
haps  as  high  as  7000°F.),  but  the  carbon  filament  as 
operated  in  practice  has  a  lower  efficiency  than  any 


132 


ABTIFICIAL  LIGHT 


other  filament.  This  is  because  the  highest  tempera¬ 
ture  at  which  it  can  be  operated  and  still  have  a  rea¬ 
sonable  life  is,  much  lower  than  that  of  metallic  fila¬ 
ments.  The  incandescent  carbon  in  the  evacuated  bulb 
sublimes  or  volatilizes  and  deposits  upon  the  bulb. 
This  decreases  the  size  of  the  filament  eventually  to 
the  breaking-point  and  the  blackening  of  the  bulb  de¬ 
creases  the  output  of  light.  The  treated  filament  was 
found  to  be  a  harder  form  of  carbon  that  did  not 
volatilize  as  rapidly  as  the  untreated  filament.  It  im¬ 
mediately  became  possible  to  operate  it  at  a  higher 
temperature  with  a  resulting  increase  of  luminous  effi¬ 
ciency.  This  “graphitized”  carbon  filament  lamp  be¬ 
came  known  as  the  gem  lamp  in  this  country  and  many 
persons  have  wondered  over  the  word  “gem.”  The 
first  two  letters  stand  for  “General  Electric”  and  the 
last  for  “metallized.”  This  lamp  was  welcomed  with 
enthusiasm  in  its  day,  but  the  day  for  carbon  fila¬ 
ments  has  passed.  The  advent  of  incandescent  lamps 
of  higher  efficiency  has  made  it  uneconomical  to  use 
carbon  lamps  for  general  lighting  purposes.  Al¬ 
though  the  treated  carbon  filament  was  a  great  im¬ 
provement,  its  reign  was  cut  short  by  the  appearance 
of  metal  filaments. 

In  1803  a  new  element  was  discovered  and  named 
tantalum.  It  is  a  dark,  lustrous,  hard  metal.  Pure 
tantalum  is  harder  than  steel;  it  may  be  drawn  into 
fine  wire;  and  its  melting-point  is  very  high  (about 
5100°F.).  It  is  seen  to  possess  properties  desirable 
for  filaments,  but  for  some  reason  it  did  not  attract 
attention  for  a  long  time.  A  century  elapsed  after  its 
discovery  before  von  Bolton  produced  the  first  tan- 


INCANDESCENT  FILAMENT  LAMPS  133 


talum  filament  lamp.  Owing  to  the  low  electrical  re¬ 
sistance  of  tantalum,  a  filament  in  order  to  operate  sat¬ 
isfactorily  on  a  standard  voltage  must  be  long  and 
thin.  This  necessitates  storing  away  a  considerable 
length  of  wire  in  the  bulb  without  permitting  the  loops 
to  come  into  contact  with  each  other.  After  the  fila¬ 
ments  have  been  in  operation  for  a  few  hundred  hours 
they  become  brittle  and  faults  develop.  When  exam¬ 
ined  under  a  microscope,  parts  of  the  filament  operated 
on  alternating  current  appear  to  be  offset.  The  ex¬ 
planation  of  this  defect  goes  deeply  into  crystalline 
structure.  The  tantalum  filament  was  quickly  fol¬ 
lowed  by  osmium  and  by  tungsten  in  this  country. 

The  osmium  filament  appeared  in  1905  and  its  in¬ 
vention  is  due  to  Welsbach,  who  had  produced  the  mar¬ 
velous  gas-mantle.  Owing  to  its  extreme  brittleness, 
osmium  was  finely  divided  and  made  into  a  paste 
of  organic  material.  The  filaments  were  squirted 
through  dies  and,  after  being  formed  and  dried,  they 
were  heated  to  a  high  temperature.  The  organic  mat¬ 
ter  disappeared  and  the  fine  metallic  particles  were 
sintered.  This  made  a  very  brittle  lamp,  but  its  high 
efficiency  served  to  introduce  it. 

In  1870  when  Scheele  discovered  a  new  element, 
known  in  this  country  as  tungsten,  no  one  realized  that 
it  was  to  revolutionize  artificial  lighting  and  to  alter 
the  course  of  some  of  the  byways  of  civilization.  This 
metal — which  is  known  as  ‘ ‘wolfram’ ’  in  Germany,  and 
to  some  extent  in  English-speaking  countries — is  one 
of  the  heaviest  of  elements,  having  a  specific  gravity  of 
19.1.  It  is  50  per  cent,  heavier  than  mercury  and 
nearly  twice  as  heavy  as  lead.  It  was  early  used  in 


134 


ARTIFICIAL  LIGHT 


German  silver  to  the  extent  of  1  or  2  per  cent,  to 
make  platinoid,  an  alloy  possessing  a  high  resistance 
which  varies  only  slightly  as  the  temperature  changes. 
This  made  an  excellent  material  for  electrical  resistors. 
The  melting-point  of  tungsten  is  about  5350°  F.,  which 
makes  it  desirable  for  filaments,  but  it  was  very  brittle 
as  prepared  in  the  early  experiments.  It  unites  very 
readily  with  oxygen  and  with  carbon  at  high  tempera¬ 
tures. 

The  first  tungsten  lamps  appeared  on  the  market  in 
1906,  but  these  contained  fragile  filaments  made  by  the 
squirting  process.  When  the  squirted  filament  of 
tungsten  powder  and  organic  matter  was  heated  in  an 
atmosphere  of  steam  and  hydrogen  to  remove  the  bind¬ 
ing  material,  a  brittle  filament  of  tungsten  was  ob¬ 
tained.  The  first  lamps  were  costly  and  fragile. 
After  years  of  organized  research  tungsten  is  now 
drawn  into  the  finest  wires,  possessing  a  tensile 
strength  perhaps  greater  than  any  other  material. 
Filaments  are  now  made  into  many  shapes  and  the 
greatest  strides  in  artificial  lighting  have  been  due 
to  scientific  research  on  a  huge  scale. 

The  achievements  which  combined  to  perfect  the 
tungsten  lamp  to  the  point  where  it  has  become  the 
mainstay  of  electric  lighting  are  not  attached  to  names 
in  the  Hall  of  Fame.  Organization  of  scientific  re¬ 
search  in  the  industrial  laboratories  is  such  that  often 
many  persons  contribute  to  the  development  of  an  im¬ 
provement.  Furthermore,  time  is  usually  required  for 
a  full  perspective  of  applications  of  scientific  knowl¬ 
edge.  In  the  early  days  organized  research  was  not 
practised  and  the  great  developments  of  those  days 


INCANDESCENT  FILAMENT  LAMPS  135 


were  the  works  of  individuals.  To-day,  even  in  pure 
science,  some  of  the  greatest  contributions  are  made 
by  industrial  laboratories;  but  sometimes  these  do  not 
become  known  to  the  public  for  many  years.  The 
whole  scheme  of  scientific  development  has  changed 
materially.  For  example,  the  story  of  the  development 
of  ductile  tungsten,  which  has  revolutionized  lighting, 
is  complex  and  more  or  less  shrouded  in  secrecy  at  the 
present  time.  Many  men  have  contributed  toward  this 
accomplishment  and  the  public  at  the  present  time 
knows  little  more  than  the  fact  that  tungsten  filaments, 
which  were  brittle  yesterday,  are  now  made  of  ductile 
tungsten  wire  drawn  into  the  finest  filaments. 

The  earlier  tungsten  filaments  were  made  by  three 
rival  processes.  By  the  first,  a  deposit  of  tungsten  was 
“flashed”  on  a  fine  carbon  filament,  the  latter  being 
eliminated  finally  by  heating  in  an  atmosphere  of  hy¬ 
drogen  and  water-vapor.  By  the  second,  colloidal 
tungsten  was  produced  by  operating  an  arc  between 
tungsten  electrodes  under  water.  The  finely  divided 
tungsten  was  gathered,  partially  dried,  and  squirted 
through  dies  to  form  filaments.  These  were  then  sin¬ 
tered.  The  third  was  the  “paste”  process  already  de¬ 
scribed.  These  methods  produced  fragile  filaments, 
but  their  luminous  efficiency  was  higher  than  that  of 
previous  ones.  However,  in  this  country  ductile  tung¬ 
sten  was  soon  on  its  way.  An  ingot  of  tungsten  is  sub¬ 
jected  to  vigorous  swaging  until  it  takes  the  form  of  a 
rod.  This  is  finally  drawn  into  wire. 

Much  of  this  development  work  was  done  by  the 
laboratories  of  the  General  Electric  Company  and  they 
were  destined  to  contribute  another  great  improve- 


136 


ARTIFICIAL  LIGHT 


ment.  The  blackening  of  the  lamp  bulbs  was  due  to 
the  evaporation  of  tungsten  from  the  filament.  All 
filaments  up  to  this  time  had  been  confined  in  evacu¬ 
ated  bulbs  and  the  low  pressure  facilitates  evaporation, 
as  is  well  known.  It  had  long  been  known  that  an  inert 
gas  in  the  bulb  would  reduce  the  evaporation  and  rem¬ 
edy  other  defects;  however,  under  these  conditions, 
there  would  be  a  considerable  loss  of  energy  through 
conduction  of  heat  by  the  gases.  In  the  vacuum  lamp 
nearly  all  the  electrical  energy  is  converted  into  ra¬ 
diant  energy,  which  is  emitted  by  the  filament  and  any 
dissipation  of  heat  is  an  energy  loss.  A  high  vacuum 
was  one  of  the  chief  aims  up  to  this  time,  but  a  radical 
departure  was  pending. 

If  an  ordinary  tungsten-lamp  bulb  be  filled  with  an 
inert  gas  such  as  nitrogen,  the  filament  may  be  oper¬ 
ated  at  a  very  much  higher  temperature  without  any 
more  deterioration  than  takes  place  in  a  vacuum  at  a 
lower  temperature.  This  gives  a  more  efficient  light 
but  a  less  efficient  lamp .  The  greater  output  of  light 
is  compensated  by  losses  by  conduction  of  heat  through 
the  gas.  In  other  words,  a  great  deal  more  energy  is 
required  by  the  filament  in  order  to  remain  at  a  given 
temperature  in  a  gas  than  in  a  vacuum.  However, 
elaborate  studies  of  the  dependence  of  heat-losses  upon 
the  size  and  shape  of  the  filament  and  of  the  physics 
of  conduction  from  a  solid  to  a  gas,  established  the 
foundation  for  the  gas-filled  tungsten  lamp.  The 
knowledge  gained  in  these  investigations  indicated 
that  a  thicker  filament  lost  a  relatively  less  percentage 
of  energy  by  conduction  than  a  thin  one  for  equal 
amounts  of  emitted  light.  However,  a  practical  fila- 


INCANDESCENT  FILAMENT  LAMPS  137 

ment  must  have  sufficient  resistance  to  be  used  safely 
on  lighting  circuits  already  established  and,  therefore, 
the  large  diameter  and  high  resistance  were  obtained 
by  making  a  helical  coil  of  a  fine  wire.  In  fact,  the 
gas-filled  tungsten  lamp  may  be  thought  of  as  an  ordi¬ 
nary  lamp  with  its  long  filament  made  into  a  short 
helical  coil  and  the  bulb  filled  with  nitrogen  or  argon 
gas. 

This  development  was  not  accidental  and  from  a 
scientific  point  of  view  it  is  not  spectacular.  It  did 
not  mark  a  new  discovery  in  the  same  sense  as  the  dis¬ 
covery  of  X-rays.  However,  it  is  an  excellent  exam¬ 
ple  of  the  great  rewards  which  come  to  systematic, 
thorough  study  of  rather  commonplace  physical  laws 
in  respect  to  a  given  condition.  Such  achievements 
are  being  duplicated  in  various  lines  in  the  laboratories 
of  the  industries.  Scientific  research  is  no  longer  mo¬ 
nopolized  by  educational  institutions.  The  most  elab¬ 
orate  and  best-equipped  laboratories  are  to  be  found 
in  the  industries  sometimes  surrounded  by  the  smoke 
and  noise  and  vigorous  activity  which  indicate  that 
achievements  of  the  laboratory  are  on  their  way  to 
mankind.  The  smoke-laden  industrial  district,  pul¬ 
sating  with  life,  is  the  proud  exhibit  of  the  present 
civilization.  It  is  the  creation  of  those  who  discover, 
organize,  and  apply  scientific  facts.  But  how  many  ap¬ 
preciate  the  debt  that  mankind  owes  not  only  to  the 
individual  who  dedicates  his  life  to  science  but  to  the 
far-sighted  manufacturer  who  risks  his  money  in  or¬ 
ganized  quest  of  new  benefits  for  mankind?  A  glimpse 
into  a  vast  organization  of  research,  which,  for  ex¬ 
ample,  has  been  mainly  responsible  for  the  progress 


138 


ARTIFICIAL  LIGHT 


of  the  incandescent  lamp  would  alter  the  attitude  of 
many  persons  toward  science  and  toward  the  large  in¬ 
dustrial  companies. 

The  progress  in  the  development  of  electric  incan¬ 
descent  lamps  is  shown  in  the  following  table,  where 
the  dates  and  values  are  more  or  less  approximate. 
It  should  be  understood  that  from  1880  to  the  present 
time  there  has  been  a  steady  progress,  which  occa¬ 
sionally  has  been  greatly  augmented  by  sudden  steps. 

Approximate  Values 


Date 

Filament 

Temperature 

Lumens  per 
watt 

1880 

Carbon 

3300°F. 

3.0 

1906 

Carbon  (graphitized) 

3400 

4.5 

1905 

Tantalum 

3550 

6.5 

1905 

Osmium 

3600 

7.5 

1906 

Tungsten  (vacuum) 

3700 

8.0 

1914 

Tungsten  (gas-filled) 

up  to  5300°F. 

10  to  25 

Throughout  the  development  of  incandescent  fila¬ 
ment  lamps  many  ingenious  experiments  were  made 
which  resulted  usually  in  light-sources  of  scientific  in¬ 
terest  but  not  of  practical  value.  One  of  the  latest 
is  the  tungsten  arc  in  an  inert  gas.  By  means  of  a 
heating  coil,  a  small  arc  is  started  between  two  elec¬ 
trodes  consisting  of  tungsten,  but  this  as  yet  has  not 
been  shown  to  be  practicable. 

Another  type  of  filament  lamp  was  developed  by 
Nernst  in  1897.  It  was  an  ingenious  application  of 
the  peculiar  properties  of  rare-earth  oxides.  His  first 
lamp  consisted  essentially  of  a  slender  rod  of  mag¬ 
nesia.  This  substance  does  not  conduct  electricity  at 


INCANDESCENT  FILAMENT  LAMPS  139 


ordinary  temperatures,  but  when  heated  to  incandes¬ 
cence  it  becomes  conducting.  Upon  sufficient  heating 
of  this  filament  by  external  means  while  a  proper  volt¬ 
age  is  impressed  upon  it,  the  electric  current  passes 
through  it  and  thereafter  this  current  will  maintain 
its  temperature.  Thus  such  a  filament  becomes  a  con¬ 
ductor  and  will  continue  to  glow  brilliantly  by  virtue 
of  the  electrical  energy  which  it  converts  into  heat. 
Later  lamps  consisted  of  “glowers”  about  one  inch 
long  made  from  a  mixture  of  zirconia  and  yttria,  and 
finally  a  mixture  of  ceria,  thoria,  and  zirconia  was 
used.  The  glower  is  heated  initially  by  a  coil  of  plat¬ 
inum  wire  located  near  it  but  not  in  contact  with  it. 
Owing  to  the  fact  that  this  glower  decreases  rapidly 
in  resistance  as  its  temperature  is  increased,  it  is 
necessary  to  place  in  series  with  it  a  substance  which 
increases  in  resistance  with  increasing  current.  This 
is  called  a  “ballasting  resistance”  and  is  usually  an 
iron  wire  in  a  glass  bulb  containing  hydrogen.  The 
heater  is  cut  out  by  an  electromagnet  when  the  glower 
goes  into  operation.  This  lamp  is  a  marvel  of  in¬ 
genuity  and  when  at  its  zenith  it  was  installed  to  a 
considerable  extent.  Its  light  is  considerably  whiter 
than  that  of  the  carbon  filament  lamps.  However,  its 
doom  was  sounded  when  metallic  filament  lamps  ap¬ 
peared. 

An  interesting  filament  was  developed  by  Parker 
and  Clark  by  using  as  a  core  a  small  filament  of  car¬ 
bon.  This  flashed  in  an  atmosphere  containing  a  vapor 
of  a  compound  of  silicon,  became  coated  with  silicon. 
This  filament  was  of  high  specific  resistance  and  ap- 


140 


ARTIFICIAL  LIGHT 


peared  to  have  promise.  It  has  not  been  introduced 
commercially  and  doubtless  it  cannot  compete  with  the 
latest  tungsten  lamps. 

Electric  incandescent  lamps  are  the  present  main¬ 
stay  of  electric  illumination  and,  it  might  be  stated,  of 
progress  in  lighting.  Wonderful  achievements  have 
been  accomplished  in  other  modes  of  lighting  and  the 
foregoing  statement  is  not  meant  to  depreciate  those 
achievements.  However,  the  incandescent  filament 
lamp  has  many  inherent  advantages.  The  light-source 
is  enclosed  in  an  air-tight  bulb  which  makes  for  a 
safe,  convenient  lamp.  The  filament  is  capable  of 
subdivision,  with  the  result  that  such  lamps  vary  from 
the  minutest  spark  of  the  smallest  miniature  lamp  to 
the  enormous  output  of  the  largest  gas-filled  tungsten 
lamp.  The  outputs  of  these  are  respectively  a  frac¬ 
tion  of  a  lumen  and  twenty-five  thousand  lumens ;  that 
is,  the  luminous  intensity  varies  from  an  equivalent 
of  a  small  fraction  of  a  standard  candle  to  a  single 
light-source  emitting  light  equivalent  to  two  thousand 
standard  candles. 

Statistics  are  cold  facts  and  are  usually  uninterest¬ 
ing  in  a  volume  of  this  character,  but  they  tell  a  story 
in  a  concise  manner.  The  development  of  the  modern 
incandescent  lamp  has  increased  the  intensity  of  light 
available  with  a  great  decrease  in  cost,  and  this  pro¬ 
gressive  development  is  shown  easily  by  tables.  For 
example,  since  the  advent  of  the  tungsten  lamp  the 
average  candle-power  and  luminous  efficiency  of  all  the 
lamps  sold  in  this  country  has  steadily  increased,  while 
the  average  wattages  of  the  lamps  have  remained  vir¬ 
tually  stationary. 


INCANDESCENT  FILAMENT  LAMPS  141 


Average  Candle-Power,  Watts,  and  Efficiency  of  All 
the  Lamps  Sold  in  This  Country 


Year 

Candle-power 

Watts 

Lumens 
per  watt 

1907 

18.0 

53 

3.33 

1908 

19.0 

53 

3.52 

1909 

21.0 

52 

3.96 

1910 

23.0 

51 

4.42 

1911 

25.0 

51 

4.82 

1912 

26.0 

49 

5.20 

1913 

29.4 

47 

6.13 

1914 

38.2 

48 

7.80 

1915 

42.2 

47 

8.74 

1916 

45.8 

49 

9.60 

1917 

48.7 

51 

10.56 

It  will  be  noted  that  the  luminous  intensity  of  in¬ 
candescent  filament  lamps  has  steadily  increased  since 
the  carbon  lamp  was  superseded,  and  that  in  a  period 
of  ten  years  of  organized  research  behind  the  tung¬ 
sten  lamp  the  luminous  efficiency  (lumens  per  watt) 
has  trebled.  In  other  words,  everything  else  remain¬ 
ing  unchanged,  the  cost  of  light  in  ten  years  was  re¬ 
duced  to  one  third.  But  the  reduction  in  cost  has 
been  more  than  this,  as  will  be  shown  later.  During 
the  same  span  of  years  the  percentage  of  carbon  fila¬ 
ment  lamps  of  the  total  filament  lamps  sold  decreased 
from  100  per  cent,  in  1907  to  13  per  cent,  in  1917. 
At  the  same  time  the  percentage  of  tungsten  (Mazda) 
lamps  increased  from  virtually  zero  in  1907  to  about  87 
per  cent,  in  1917.  The  tantalum  lamp  had  no  oppor¬ 
tunity  to  become  established,  because  the  tungsten  lamp 
followed  its  appearance  very  closely.  In  1910  the 


142  ARTIFICIAL  LIGHT 

sales  of  the  former  reached  their  highest  mark,  which 
was  only  3.5  per  cent,  of  all  the  lamps  sold  in  the  United 
States.  From  a  lowly  beginning  the  number  of  in¬ 
candescent  filament  lamps  sold  for  use  in  this  country 
has  grown  rapidly,  reaching  nearly  two  hundred  mil¬ 
lion  in  1919. 


XI 


THE  LIGHT  OF  THE  FUTURE 

In  viewing  the  development  of  artificial  light  and 
its  manifold  effects  upon  the  activities  of  mankind,  it 
is  natural  to  look  into  the  future.  Jules  Verne  pos¬ 
sessed  the  advantage  of  being  able  to  write  into  fiction 
what  his  riotous  imagination  dictated,  and  so  much  of 
what  he  pictured  has  come  true  that  his  success  tempts 
one  to  do  likewise  in  prophesying  the  future  of  light¬ 
ing.  Surely  a  forecast  based  alone  upon  the  past 
achievements  and  the  present  indications  will  fall 
short  of  the  actual  realizations  of  the  future!  If  the 
imagination  is  permitted  to  view  the  future  without 
restrictions,  many  apparently  far-fetched  schemes  may 
be  devised.  It  may  be  possible  to  turn  to  nature’s  sup¬ 
ply  of  daylight  and  to  place  some  of  it  in  storage  for 
night  use.  One  millionth  part  of  daylight  released 
as  desired  at  night  would  illuminate  sufficiently  all  of 
man’s  nocturnal  activities.  The  fictionist  need  not 
heed  the  scientist’s  inquiry  as  to  how  this  daylight 
would  be  bottled.  Instead  of  giving  time  to  such  in¬ 
quiries  he  would  pass  on  to  another  scheme,  whereby 
the  earth  would  be  belted  with  optical  devices  so  that 
day  could  never  leave.  When  the  sun  was  shining  in 
China  its  light  would  be  gathered  on  a  large  scale  and 
sent  eastward  and  westward  in  these  great  optical 
“pipe-lines”  to  the  regions  of  darkness,  thus  banish- 

143 


144 


ARTIFICIAL  LIGHT 


ing  night  forever.  The  writer  of  fiction  need  not 
bother  with  a  consideration  of  the  economic  situation 
which  would  demand  such  efforts.  This  line  of  con¬ 
jecture  is  interesting,  for  it  may  suggest  possibilities 
toward  which  the  present  trend  of  artificial  lighting 
does  not  point;  however,  the  author  is  constrained  to 
treat  the  future  of  light-production  on  a  somewhat 
more  conservative  basis. 

At  the  present  time  the  light-source  of  chief  inter¬ 
est  in  electric  lighting  is  the  incandescent  filament 
lamp;  but  its  luminous  efficiency  is  limited,  as  has  been 
shown  in  a  previous  chapter.  When  light  is  emitted 
by  virtue  of  its  temperature  much  invisible  radiant 
energy  accompanies  the  visible  energy.  The  highest 
luminous  efficiency  attainable  by  pure  temperature 
radiation  will  be  reached  when  the  temperature  of  a 
normal  radiator  reaches  the  vicinity  of  10,000° F.  to 
11,000° F.  The  melting-points  of  metals  are  much 
lower  than  this.  The  tungsten  filament  in  the  most 
efficient  lamps  employing  it  is  operating  near  its  melt¬ 
ing-point  at  the  present  time.  Carbon  is  a  most  at¬ 
tractive  element  in  respect  to  melting-point,  for  it 
melts  at  a  temperature  between  6000°F.  and  7000°F. 
Even  this  is  far  below  the  most  efficient  temperature 
for  the  production  of  light  by  means  of  pure  tempera¬ 
ture  radiation.  There  are  possibilities  of  higher  effi¬ 
ciency  being  obtained  by  operating  arcs  or  filaments 
under  pressure;  however,  it  appears  that  highly  effi¬ 
cient  light  of  the  future  will  result  from  a  radical 
departure. 

Scientists  are  becoming  more  and  more  intimate  with 
the  structure  of  matter.  They  are  learning  secrets 


THE  LIGHT  OF  THE  FUTURE 


145 


every  year  which  apparently  are  leading  to  a  funda¬ 
mental  knowledge  of  the  subject.  When  these  mys¬ 
teries  are  solved,  who  can  say  that  man  will  not  be 
able  to  create  elements  to  suit  his  needs,  or  at  least 
to  alter  the  properties  of  the  elements  already  avail¬ 
able?  If  he  could  so  alter  the  mechanism  of  radia¬ 
tion  that  a  hot  metal  would  radiate  no  invisible  en¬ 
ergy,  he  would  have  made  a  tremendous  stride  even 
in  the  production  of  light  by  virtue  of  high  tempera¬ 
ture.  This  property  of  selective  radiation  is  pos¬ 
sessed  by  some  elements  to  a  slight  degree,  but  if  treat¬ 
ment  could  enhance  this  property,  luminous  efficiency 
would  be  greatly  increased.  Certainly  the  principle 
of  selectivity  is  a  byway  of  possibilities. 

A  careful  study  of  commonplace  factors  may  result 
in  a  great  step  in  light-production  without  the  crea¬ 
tion  of  new  elements  or  compounds,  just  as  such  a  pro¬ 
cedure  doubled  the  luminous  efficiency  of  the  tungsten 
filament  when  the  gas-filled  lamp  appeared.  There 
are  a  few  elements  still  missing,  according  to  the  Pe¬ 
riodic  Law  which  has  been  so  valuable  in  chemistry. 
When  these  turn  up,  they  may  be  found  to  possess 
valuable  properties  for  light-production;  but  this  is 
a  discouraging  byway. 

It  is  natural  to  inquire  whether  or  not  any  mode  of 
light-production  now  in  use  has  a  limiting  luminous 
efficiency  approaching  the  ultimate  limit  which  is  im¬ 
posed  by  the  visibility  of  radiation.  The  eye  is  able 
to  convert  radiant  energy  of  different  wave-lengths 
into  certain  fixed  proportions  of  light.  For  example, 
radiant  energy  of  such  a  wave-length  as  to  excite  the 
sensation  of  yellow-green  is  the  most  efficient  and  one 


146 


ARTIFICIAL  LIGHT 


watt  of  this  energy  is  capable  of  being  converted  by 
the  visual  apparatus  into  about  625  lumens  of  light. 
Is  this  efficiency  of  conversion  of  the  visual  apparatus 
everlastingly  fixed?  For  the  answer  it  is  necessary 
to  turn  to  the  physiologist,  and  doubtless  he  would  sug¬ 
gest  the  curbing  of  the  imagination.  But  is  it  un¬ 
thinkable  that  the  visual  processes  will  always  be  be¬ 
yond  the  control  of  man?  However,  to  turn  again  to 
the  physics  of  light-production,  there  are  still  several 
processes  of  producing  light  which  are  appealing. 

Many  years  ago  Geissler,  Crookes,  and  other  scien¬ 
tists  studied  the  spectra  of  gases  excited  to  incandes¬ 
cence  by  the  electric  discharge  in  so-called  vacuum 
tubes.  The  gases  are  placed  in  transparent  glass  or 
quartz  tubes  at  rather  low  pressures  and  a  high  volt¬ 
age  is  impressed  upon  the  ends  of  these  tubes.  When 
the  pressure  is  sufficiently  low,  the  gases  will  glow  and 
emit  light.  Twenty-eight  years  ago,  D.  McFarlan 
Moore  developed  the  nitrogen  tube,  which  was  actually 
installed  in  various  places.  But  there  is  such  a  loss 
of  energy  near  the  cathode  that  short  “vacuum”  tubes 
of  this  character  are  very  inefficient  producers  of  light. 
Efficiency  is  greatly  increased  by  lengthening  the  tubes, 
so  Moore  used  tubes  of  great  length  and  a  rather  high 
voltage.  As  a  tube  of  this  sort  is  used,  the  gas  grad¬ 
ually  disappears  and  it  must  be  replenished.  In  or¬ 
der  to  replenish  the  gas,  Moore  devised  a  valve  for 
feeding  gas  automatically.  An  advantage  of  this  mode 
of  light-production  is  that  the  color  or  quality  of  the 
light  may  be  varied  by  varying  the  gas  used.  Nitro¬ 
gen  yields  a  pinkish  light;  neon  an  orange  light;  and 
carbon  dioxide  a  white  light.  Moore’s  carbon-dioxide 


THE  LIGHT  OF  THE  FUTURE 


147 


tube  is  an  excellent  substitute  for  daylight  and  has 
been  used  for  the  discrimination  of  colors  where  this 
is  an  important  factor.  However,  for  this  purpose 
devices  utilizing  color-screens  which  alter  the  light 
from  the  tungsten  lamp  to  a  daylight  quality  are  being 
used  extensively. 

The  vacuum-tube  method  of  producing  light  has  an 
advantage  in  the  selection  of  a  gas  among  a  large  num¬ 
ber  of  possibilities,  and  some  of  the  color  effects  of 
the  future  may  be  obtained  by  means  of  it.  Claude 
has  lately  worked  on  light-production  by  vacuum  tubes 
and  has  combined  the  neon  tube  with  the  mercury- 
vapor  tube.  The  spectrum  of  neon  to  a  large  extent 
compensates  for  the  absence  of  red  light  in  the  mer¬ 
cury  spectrum,  with  a  result  that  the  mixture  produces 
a  more  satisfactory  light  than  that  of  either  tube. 
However,  this  mode  of  light-production  has  not  proved 
practicable  in  its  present  state  of  development.  Fun¬ 
damentally  the  limitations  are  those  of  the  inherent 
spectral  characteristics  of  gases.  Doubtless  the  pos¬ 
sibilities  of  the  mechanisms  of  the  tubes  and  of  com¬ 
bining  various  gases  have  not  been  exhausted.  Fur¬ 
thermore,  if  man  ever  becomes  capable  of  controlling 
to  some  extent  the  structure  of  elements  and  of  com¬ 
pounds,  this  method  of  light-production  is  perhaps 
more  promising  than  others  of  the  present  day. 

There  is  another  attractive  method  of  producing 
light  and  it  has  not  escaped  the  writer  of  fiction.  H. 
G.  Wells,  with  his  rare  skill  and  with  the  license  so 
often  envied  by  the  writer  of  facts,  has  drawn  upon 
the  characteristics  of  fluorescence  and  phosphores¬ 
cence.  In  his  story  “The  First  Men  in  the  Moon,”  the 


148 


ARTIFICIAL  LIGHT 


inhabitants  of  the  moon  illuminate  their  caverns  by 
utilizing  this  phenomenon.  A  fluorescent  liquid  was 
prepared  in  large  quantities.  It  emitted  a  brilliant 
phosphorescent  glow  and  when  it  splashed  on  the  feet 
of  the  earth-men  it  felt  cold,  but  it  glowed  for  a  long 
time.  This  is  a  possibility  of  the  future  and  many 
have  had  visions  of  such  lighting.  If  the  ceiling  of  a 
coal-mine  was  lined  with  glowing  fireflies  or  with  phos¬ 
phorescent  material  excited  in  some  manner,  it  would 
be  possible  to  see  fairly  well  with  the  dark-adapted 
eyes. 

This  leads  to  the  class  of  phenomena  included  under 
the  general  term  “luminescence.”  The  definition  of 
this  term  is  not  thoroughly  agreed  upon,  but  light  pro¬ 
duced  in  this  manner  does  not  depend  upon  tempera¬ 
ture  in  the  sense  that  a  glowing  tungsten  filament  emits 
light  because  it  is  sufficiently  hot.  A  phosphorus 
match  rubbed  in  the  moist  palm  of  the  hand  is  seen  to 
glow,  although  it  is  at  an  ordinary  temperature.  This 
may  be  termed  “chemi -luminescence.”  Sidot  blende, 
Balmain’s  paint,  and  many  other  compounds,  when 
illuminated  with  ordinary  light,  and  especially  with 
ultra-violet  and  violet  rays,  will  continue  to  glow  for 
a  long  time.  Despite  their  brightness  they  will  be  cold 
to  the  touch.  This  phenomenon  would  be  termed 
“photo-luminescence,”  although  it  is  better  known  as 
“phosphorescence.”  It  should  be  noted  that  the  lat¬ 
ter  term  was  carelessly  originated,  for  phosphorus  has 
nothing  to  do  with  it.  The  glow  of  the  Geissler  tube 
or  electrically  excited  gas  at  low  pressure  would  be 
an  example  of  “electro-luminescence.”  The  luminos¬ 
ity  of  various  salts  in  the  Bunsen-flame  is  due  to  so- 


THE  LIGHT  OF  THE  FUTURE 


149 


called  luminescence  and  there  are  many  other  exam¬ 
ples  of  light-production  which  are  included  in  the  same 
general  class.  Inasmuch  as  light  is  emitted  from  com¬ 
paratively  cold  bodies  in  these  cases,  it  is  popularly 
known  as  “cold”  light. 

There  are  many  instances  of  light  being  emitted 
without  being  accompanied  by  appreciable  amounts  of 
invisible  radiant  energy  and  it  is  natural  to  hope  for 
practical  possibilities  in  this  direction.  As  yet  little 
is  known  regarding  the  efficiency  of  light-production 
by  phosphorescence.  The  luminous  efficiency  of  the 
radiant  energy  emitted  by  phosphorescent  substances 
has  been  studied,  but  it  seems  strange  that  among  the 
vast  works  on  phosphorescent  phenomena,  scarcely  any 
mention  is  made  of  the  efficiency  of  producing  light  in 
this  manner.  For  example,  assume  that  phosphores¬ 
cent  zinc  sulphide  is  excited  by  the  light  from  a  mer¬ 
cury-arc.  All  the  energy  falling  upon  it  is  not  capable 
of  exciting  phosphorescence,  as  may  be  readily  shown. 
Assuming  that  a  known  amount  of  radiant  energy  of  a 
certain  wave-length  has  been  permitted  to  fall  upon 
the  phosphorescent  material,  then  in  the  dark  the  lat¬ 
ter  may  be  seen  to  glow  for  a  long  time.  An  interest¬ 
ing  point  to  investigate  is  the  relation  of  the  output 
to  input ;  that  is,  the  ratio  of  the  total  emitted  light  to 
the  total  exciting  energy.  This  is  a  neglected  aspect  in 
the  study  of  light-production  by  this  means. 

The  firefly  has  been  praised  far  and  wide  as  the  ideal 
light-source.  It  is  an  efficient  radiator  of  light,  for  its 
light  is  “cold” ;  that  is,  it  does  not  appear  to  be  accom¬ 
panied  by  invisible  radiant  energy.  But  little  is  said 
about  its  efficiency  as  a  light-producer.  Who  knows 


150 


ARTIFICIAL  LIGHT 


how  much  fuel  its»lighting-plant  consumes  ?  The  chem¬ 
istry  of  light-production  by  living  organisms  is  being 
unraveled  and  this  part  of  the  phenomenon  will  likely 
be  laid  bare  before  long.  For  an  equal  amount  of 
energy  radiated,  the  firefly  emits  a  great  many  times 
more  light  than  the  most  efficient  lamp  in  use  at  the 
present  time,  but  before  the  firefly  is  pronounced  ideal, 
the  efficiency  of  its  light-producing  process  must  be 
known. 

There  are  many  ways  of  exciting  phosphorescence 
and  fluorescence,  the  latter  being  merely  an  unendur¬ 
ing  phosphorescence,  which  ceases  when  the  exciting 
energy  is  cut  off.  Ultra-violet,  violet,  and  blue  rays 
are  generally  the  most  effective  radiant  energy  for 
excitation  purposes.  X-rays  and  the  high-frequency 
discharge  are  also  powerful  excitants.  As  already 
stated,  virtually  nothing  is  known  of  the  efficiency  of 
this  mode  of  light-production  or  of  the  mechanism 
within  the  substance,  but  on  the  whole  it  is  a  remark¬ 
able  phenomenon. 

Radium  is  also  a  possibility  in  light-production  and 
in  fact  has  been  practically  employed  for  this  purpose 
for  several  years.  It  or  one  of  its  compounds  is  mixed 
with  a  phosphorescent  substance  such  as  zinc  sulphide 
and  the  latter  glows  continuously.  Inasmuch  as  the 
life  of  some  of  the  radium  products  is  very  long,  such 
a  method  of  illuminating  watch-dials,  scales  of  instru¬ 
ments,  etc.,  is  very  practicable  where  they  are  to  be 
read  by  eyes  adapted  to  darkness  and  consequently 
highly  sensitive  to  light.  Whether  or  not  radium  will 
be  manufactured  by  the  ton  in  the  future  can  only  be 
conjectured. 


THE  LIGHT  OF  THE  FUTURE 


151 


Owing  to  the  limitations  imposed  by  physical  laws 
of  radiation  and  by  the  physiological  processes  of 
vision,  the  highest  luminous  efficiency  obtainable  by 
heating  solid  materials  is  only  about  15  per  cent,  of 
the  luminous  efficiency  of  the  most  luminous  radiant 
energy.  At  present  there  are  no  materials  available 
which  may  be  operated  at  the  temperature  necessary 
to  reach  even  this  efficiency.  Great  progress  in  the 
future  of  light-production  as  indicated  by  present 
knowledge  appears  to  lie  in  the  production  of  light 
which  is  unaccompanied  by  invisible  radiant  energy. 
At  present  such  phenomena  as  fluorescence,  phosphor¬ 
escence,  the  light  of  the  firefly,  cliemi-luminescence,  etc., 
are  examples  of  this  kind  of  light-production.  Of 
course,  if  science  ever  obtains  control  over  the  consti¬ 
tution  of  matter,  many  difficulties  will  disappear  ;  for 
then  man  will  not  be  dependent  upon  the  elements  and 
compounds  now  available  but  will  be  able  to  modify 
them  to  suit  his  needs. 


XII 

LIGHTING  THE  STREETS 

In  this  age  of  brilliantly  lighted  boulevards  and 
4 ‘great  white  ways”  flooded  with  light  from  shop-win¬ 
dows,  electric  signs,  and  street-lamps,  it  is  difficult  to 
visualize  the  gloom  which  shrouded  the  streets  a  cen¬ 
tury  ago.  As  the  belated  pedestrian  walks  along  the 
suburban  highways  in  comparative  safety  under  ade¬ 
quate  artificial  lighting,  he  will  realize  the  great  influ¬ 
ence  of  artificial  light  upon  civilization  if  he  recalls 
that  not  more  than  two  centuries  ago  in  London 

it  was  a  common  practice  .  .  .  that  a  hundred  or  more 
in  a  company,  young  and  old,  would  make  nightly  in¬ 
vasions  upon  houses  of  the  wealthy  to  the  intent  to 
rob  them  and  that  when  night  wTas  come  no  man  durst 
adventure  to  walk  in  the  streets. 

Inhabitants  of  the  cities  of  the  present  time  are  in¬ 
clined  to  think  that  crime  is  common  on  the  streets  at 
night,  but  what  would  it  be  without  adequate  artificial 
light!  Two  centuries  ago  in  a  city  like  London  a  smok¬ 
ing  grease-lamp,  a  candle,  or  a  basket  of  pine  knots 
here  and  there  afforded  the  only  street-lighting,  and 
these  were  extinguished  by  eleven  o’clock.  Lawless¬ 
ness  was  hatched  and  hidden  by  darkness,  and  even  the 
lantern  or  torch  served  more  to  mark  the  victim  than 

152 


LIGHTING  THE  STREETS 


153 


to  protect  him.  It  has  been  said  in  describing  the  con¬ 
ditions  of  the  age  of  dark  streets  that  everybody  signed 
his  will  and  was  prepared  for  death  before  he  left  his 
home.  By  comparison  with  the  present,  one  is  again 
encouraged  to  believe  that  the  world  grows  better. 
Doubtless,  artificial  light  projected  into  the  crannies 
has  had  something  to  do  with  this  change. 

Adequate  street-lighting  is  really  a  product  of  the 
twentieth  century,  but  throughout  the  nineteenth  cen¬ 
tury  progress  was  steadily  made  from  the  beginning 
of  gas-lighting  in  1807.  In  preceding  centuries  crude 
lighting  was  employed  here  and  there  but  not  generally 
by  the  public  authorities.  In  the  earliest  centuries  of 
written  history  little  is  said  of  street-lighting.  In 
those  days  man  was  not  so  much  inclined  to  improve 
upon  nature,  beyond  protecting  himself  from  the  ele¬ 
ments,  and  he  lighted  the  streets  more  as  a  festive  out¬ 
burst  than  as  an  economic  proposition.  Nevertheless, 
in  the  early  writings  occasionally  there  are  indications 
that  in  the  centers  of  advanced  civilization  some  efforts 
were  made  to  light  the  streets. 

The  old  Syrian  city  of  Antioch,  which  in  the  fourth 
century  of  the  Christian  era  contained  about  four  hun¬ 
dred  thousand  inhabitants,  appears  to  have  had  lighted 
streets.  Libanius,  who  lived  in  the  early  years  of  that 
century,  wrote : 

The  light  of  the  sun  is  succeeded  by  other  lights, 
which  are  far  superior  to  the  lamps  lighted  by  Egyp¬ 
tians  on  the  festival  of  Minerva  of  Sais.  The  night 
with  us  differs  from  the  day  only  in  the  appearance 
of  the  light;  with  regard  to  labor  and  employment, 
everything  goes  on  well. 


154 


ARTIFICIAL  LIGHT 


Although  apparently  labor  was  not  on  a  strike,  the 
soldiers  caused  disturbances,  for  in  another  passage  he 
tells  of  riotous  soldiers  who 

cut  with  their  swords  the  ropes  from  which  were  sus¬ 
pended  the  lamps  that  afforded  light  in  the  night-time, 
to  show  that  the  ornaments  of  the  city  ought  to  give 
way  to  them. 

Another  writer  in  describing  a  dispute  between  two 
religious  adherents  of  opposed  creeds  stated  that  they 
quarreled  “till  the  streets  were  lighted”  and  the  crowd 
of  onlookers  broke  up,  but  not  until  they  ‘  ‘  spat  in  each 
other’s  face  and  retired.”  Thus  it  is  seen  that  artifi¬ 
cial  light  and  civilization  may  advance,  even  though 
some  human  traits  remain  fundamentally  unchanged. 

Throughout  the  next  thousand  years  there  was  lit¬ 
tle  attempt  to  light  the  streets.  Iron  baskets  of  burn¬ 
ing  wood,  primitive  oil-lamps,  and  candles  were  used  to 
some  extent,  but  during  all  these  centuries  there  was 
no  attempt  on  the  part  of  the  government  or  of  indi¬ 
viduals  to  light  the  streets  in  an  organized  manner.  In 
1417  the  Mayor  of  London  ordained  “lanthorns  with 
lights  to  bee  hanged  out  on  the  winter  evenings  be¬ 
twixt  Hallowtide  and  Candlemasse.”  This  was  dur¬ 
ing  the  festive  season,  so  perhaps  street-lighting  was 
not  the  sole  aim.  Early  in  the  sixteenth  century,  the 
streets  of  Paris  being  infested  with  robbers,  the  in¬ 
habitants  were  ordered  to  keep  lights  burning  in  the 
windows  of  all  houses  that  fronted  on  the  streets. 

For  about  three  centuries  the  citizens  of  London, 
and  doubtless  of  Paris  and  of  other  cities,  were  re¬ 
minded  from  time  to  time  in  official  mandates  “on 


LIGHTING  THE  STREETS 


155 


pains  and  penalties  to  hang  out  their  lanthorns  at  the 
appointed  time.  ”  The  watchman  in  long  coat  with 
halberd  and  lantern  in  hand  supplemented  these  man¬ 
dates  as  he  made  his  rounds  by, 

A  light  here,  maids,  hang  out  your  lights, 

And  see  your  horns  be  clear  and  bright, 

That  so  your  candle  clear  may  shine, 
Continuing  from  six  till  nine; 

That  honest  men  that  walk  along 
May  see  to  pass  safe  without  wrong. 

In  1668,  when  some  regulations  were  made  for  im¬ 
proving  the  streets  of  London,  the  inhabitants  were 
ordered  “for  the  safety  and  peace  of  the  city  to  hang 
out  candles  duly  to  the  accustomed  hour.”  Appar¬ 
ently  this  method  of  obtaining  lighting  for  the  streets 
was  not  met  by  the  enthusiastic  support  of  the  people, 
for  during  the  next  few  decades  the  Lord  Mayor  was 
busy  issuing  threats  and  commands.  In  1679  he  pro¬ 
claimed  the  “neglect  of  the  inhabitants  of  this  city  in 
hanging  and  keeping  out  their  lights  at  the  accustomed 
hours,  according  to  the  good  and  ancient  usage  of  this 
City  and  Acts  of  the  Common  Council  on  that  behalf.  ’  ’ 
The  result  of  this  neglect  was  “when  nights  darkened 
the  streets  then  wandered  forth  the  sons  of  Belial, 
flown  with  insolence  and  wine.” 

In  1694  Hemig  patented  a  reflector  which  partially 
surrounded  the  open  flame  of  a  whale-oil  lamp  and  pos¬ 
sessed  a  hole  in  the  top  which  aided  ventilation.  He 
obtained  the  exclusive  rights  of  lighting  London  for  a 
period  of  years  and  undertook  to  place  a  light  before 
every  tenth  door,  between  the  hours  of  six  and  twelve 


156 


ARTIFICIAL  LIGHT 


o’clock,  from  Michaelmas  to  Lady  Hay.  His  effort 
was  a  worthy  one,  but  he  was  opposed  by  a  certain  fac¬ 
tion,  which  was  successful  in  obtaining  a  withdrawal  of 
his  license  in  1716.  Again  the  burden  of  lighting  the 
streets  was  thrust  upon  the  residents  and  fines  were 
imposed  for  negligence  in  this  respect.  But  this  pro¬ 
cedure  after  a  few  more  years  of  desultory  lighting 
was  again  found  to  be  unsatisfactory. 

In  1729  certain  individuals  contracted  to  light  the 
streets  of  London  by  taxing  the  residents  and  paid  the 
city  for  this  monopoly.  Householders  were  permitted 
to  hang  out  a  lantern  or  a  candle  or  to  pay  the  com¬ 
pany  for  doing  so.  But  robberies  increased  so  rap¬ 
idly  that  in  1736  the  Lord  Mayor  and  Common  Coun¬ 
cil  petitioned  Parliament  to  erect  lamps  for  lighting 
the  city.  An  act  was  passed  accordingly,  giving  them 
the  privilege  to  erect  lamps  where  they  saw  fit  and  to 
burn  them  from  sunset  to  sunrise.  A  charge  was  made 
to  the  residents,  on  a  sliding  scale  depending  upon  the 
rate  of  rental  of  the  houses.  As  a  consequence  five 
thousand  lamps  were  soon  installed.  In  1738  there 
were  fifteen  thousand  street  lamps  in  London  and  they 
were  burned  an  average  of  five  thousand  hours  an¬ 
nually. 

In  the  annals  of  these  early  times  street-lighting  is 
almost  invariably  the  result  of  an  attempt  to  reduce 
the  number  of  robberies  and  other  crimes.  In  appeal¬ 
ing  for  more  street-lamps  in  1744  the  Lord  Mayor  and 
aldermen  of  London  in  a  petition  to  the  king,  stated 

that  divers  confederacies  of  great  numbers  of  evil-dis¬ 
posed  persons,  armed  with  bludgeons,  pistols,  cut¬ 
lasses,  and  other  dangerous  weapons,  infest  not  only 


LIGHTING  THE  STREETS 


157 


the  private  lanes  and  passages,  but  likewise  the  pub¬ 
lic  streets  and  places  of  public  concourse,  and  commit 
most  daring  outrages  upon  the  persons  of  your  Maj¬ 
esty’s  good  subjects,  whose  affairs  oblige  them  to  pass 
through  the  streets,  by  terrifying,  robbing  and  wound¬ 
ing  them;  and  these  facts  are  frequently  perpetrated 
at  such  times  as  were  heretofore  deemed  hours  of 
security. 

It  has  already  been  seen  that  gas-lighting  was  intro¬ 
duced  in  the  streets  of  London  for  the  first  time  in 
1807.  This  marks  the  real  beginning  of  public-service 
lighting  companies.  In  the  next  decade  interest  in 
street-lighting  by  means  of  gas  was  awakened  on 
the  Continent,  and  it  was  not  long  before  this  new 
phase  of  civilization  was  well  under  way.  Although 
this  first  gas-lighting  was  done  by  the  use  of  open 
flames,  it  was  a  great  improvement  over  all  the  pre¬ 
ceding  efforts.  Lawlessness  did  not  disappear  en¬ 
tirely,  of  course,  and  perhaps  it  never  will,  but  it 
skulked  in  the  back  streets.  A  controlling  influence 
had  now  appeared. 

But  early  innovations  in  lighting  did  not  escape 
criticism  and  opposition.  In  fact,  innovations  to-day 
are  not  always  received  by  unanimous  consent.  There 
were  many  in  those  early  days  who  felt  that  what  was 
good  for  them  should  be  good  enough  for  the  younger 
generation.  The  descendants  of  these  opponents  are 
present  to-day  but  fortunately  in  diminishing  numbers. 
It  has  been  shown  that  in  Philadelphia  in  1833  a  pro¬ 
posal  to  install  a  gas-plant  was  met  with  a  protest 
signed  by  many  prominent  citizens.  A  few  para¬ 
graphs  of  an  article  entitled  4  4  Arguments  against 
Light”  which  appeared  in  the  Cologne  Zeitung  in  1816 


158  ARTIFICIAL  LIGHT 

indicate  the  character  of  the  objections  raised  against 
street-lighting. 

1  From  the  theological  standpoint:  Artificial  illum¬ 

ination  is  an  attempt  to  interfere  with  the  divine 
plan  of  the  world,  which  has  preordained  dark¬ 
ness  during  the  night-time. 

2  From  the  judicial  standpoint:  Those  people  who 

do  not  want  light  ought  not  to  be  compelled  to  pay 
for  its  use. 

3  From  the  medical  standpoint:  The  emanations  of 

illuminating  gas  are  injurious.  Moreover,  illum¬ 
inated  streets  would  induce  people  to  remain  later 
out  of  doors,  leading  to  an  increase  in  ailments 
caused  by  colds. 

4  From  the  moral  standpoint:  The  fear  of  darkness 

will  vanish  and  drunkenness  and  depravity  in¬ 
crease. 

5  From  the  viewpoint  of  the  police:  The  horses  will 

get  frightened  and  the  thieves  emboldened. 

6  From  the  point  of  view  of  national  economy :  Great 

sums  of  money  will  be  exported  to  foreign  coun¬ 
tries. 

7  From  the  point  of  view  of  the  common  people :  The 

constant  illumination  of  streets  by  night  will  rob 
festive  illuminations  of  their  charm. 

The  foregoing  objections  require  no  comment,  for 
they  speak  volumes  pertaining  to  the  thoughts  and  ac¬ 
tivities  of  men  a  century  ago.  It  is  difficult  to  believe 
that  civilization  has  traveled  so  far  in  a  single  cen¬ 
tury,  but  from  this  early  beginning  of  street-lighting 
social  progress  received  a  great  impetus.  Artificial 
light-sources  were  feeble  at  that  time,  but  they  made 
the  streets  safer  and  by  means  of  them  social  inter¬ 
course  was  exteij^ed.  The  people  increased  their 


LIGHTING  THE  STREETS 


159 


hours  of  activity  and  commerce,  industry,  and  knowl¬ 
edge  grew  apace. 

The  open  gas-jet  and  kerosene-flame  lamps  held  forth 
on  the  streets  until  within  the  memory  of  middle-aged 
persons  of  to-day.  The  lamplighter  with  his  ladder 
is  still  fresh  in  memory.  Many  of  the  towns  and  vil¬ 
lages  have  never  been  lighted  by  gas,  for  they  stepped 
from  the  oil-lamp  to  the  electric  lamp.  The  gas-man¬ 
tle  has  made  it  possible  for  gas-lighting  to  continue 
as  a  competitor  of  electric-lighting  for  the  streets. 

In  1877  Mr.  Brush  illuminated  the  Public  Square  of 
Cleveland  with  a  number  of  arc-lamps,  and  these  met 
with  such  success  that  within  a  short  time  two  hundred 
and  fifty  thousand  open-arc  lamps  were  installed  in  this 
country,  involving  an  investment  of  millions  of  dol¬ 
lars.  Adding  to  this  investment  a  much  greater  one 
in  central-station  equipment,  a  very  large  investment 
is  seen  to  have  resulted  from  this  single  development 
in  lighting. 

This  open-arc  lamp  was  the  first  powerful  light- 
source  available  and,  appearing  several  years  before 
the  gas-mantle,  it  threatened  to  monopolize  street¬ 
lighting.  It  consumed  about  500  watts  and  had  a  maxi¬ 
mum  luminous  intensity  of  about  1200  candles  at  an 
angle  of  about  45  degrees.  Its  chief  disadvantage  was 
its  distribution  of  light,  mainly  at  this  angle  of  45  de¬ 
grees,  which  resulted  in  a  spot  of  light  near  the  lamp 
and  little  light  at  a  distance.  A  satisfactory  street¬ 
lighting  unit  must  emit  its  light  chiefly  just  below  the 
horizontal  in  those  cases  where  the  lamps  must  be 
spaced  far  apart  for  economical  reasons.  On  refer¬ 
ring  to  the  chapter  on  the  electric  arc  it  will  be  seen 


160 


ARTIFICIAL  LIGHT 


that  the  upper  (positive)  carbon  of  the  open-arc  emits 
most  of  the  light.  Thus  most  of  the  light  tends  to  be 
sent  downward,  but  the  lower  carbon  obstructs  some 
of  this  with  a  resulting  dark  spot  beneath  the  lamp. 

The  gas-mantle  followed  closely  after  the  arrival  of 
the  carbon  arc  and  is  responsible  for  the  existence  of 
gas-ligliting  on  the  streets  at  the  present  time.  It  is  a 
large  source  of  light  and  therefore  its  light  cannot  be 
controlled  by  modern  accessories  as  well  as  the  light 
from  smaller  sources,  such  as  the  arc  or  concentrated- 
filament  lamp.  As  a  consequence,  there  is  marked  un¬ 
evenness  of  illumination  along  the  streets  unless  the 
gas-mantle  units  are  spaced  rather  closely.  Even  with 
the  open-arc,  without  special  light-controlling  equip¬ 
ment  there  is  about  a  thousand  times  the  intensity  near 
the  lamps  when  placed  on  the  corners  of  the  block  as 
there  is  midway  between  them. 

In  1879  the  incandescent  filament  lamp  was  intro¬ 
duced  and  it  began  to  appear  on  the  streets  in  a  short 
time.  It  was  a  feeble,  inefficient  light-source,  com¬ 
pared  with  the  arc-lamp,  but  it  had  the  advantage  of 
being  installed  on  a  small  bracket.  As  a  consequence 
of  simplicity  of  operation,  the  incandescent  lamp  was 
installed  to  a  considerable  extent,  especially  in  the 
suburban  districts. 

The  open-arc  lamp  possessed  the  disadvantage  of 
emitting  a  very  unsteady  light  and  of  consuming  the 
carbons  so  rapidly  that  daily  trimming  was  often 
necessary.  In  1893  the  enclosed  arc  appeared  and  al¬ 
though  it  consumed  as  much  electrical  energy  as  the 
open-arc  and  emitted  considerably  less  light,  it  pos¬ 
sessed  the  great  advantage  of  operating  a  week  with- 


In  lobby  of  Madison  Square  Garden  ACCURATE  COLOR-MATCHING 


MODERN  STREET  LIGHTING 

Tunnels  of  light  boring  through  the  darkness  provide  safe  channels  for  modern  traffic 


LIGHTING  THE  STREETS 


161 


out  requiring  a  renewal  of  carbons.  By  surrounding 
the  arc  by  means  of  a  glass  globe,  little  oxygen  could 
come  in  contact  with  the  carbons  and  they  were  not 
consumed  very  rapidly.  The  light  was  fairly  steady 
and  these  arcs  operated  satisfactorily  on  alternating 
current.  The  latter  feature  simplified  the  generating 
and  distributing  equipment  of  the  central  station. 

The  magnetite  or  luminous  arc-lamp  next  appeared 
and  met  with  considerable  success.  It  was  more  effi¬ 
cient  than  the  preceding  lamps  but  was  handicapped 
by  being  solely  a  direct-current  device.  Those  familiar 
with  the  generation  and  distribution  of  electricity  will 
realize  this  disadvantage.  However,  its  luminous  in¬ 
tensity  just  below  the  horizontal  was  about  700  can¬ 
dles  and  its  general  distribution  of  light  was  fairly 
satisfactory.  Later  the  flame-arcs  began  to  appear 
and  they  were  installed  to  some  extent.  The  arc-lamp 
has  served  well  in  street-lighting  from  the  year  1877, 
when  the  open-arc  was  introduced,  until  the  present 
time,  when  the  luminous-arc  is  the  chief  survivor  of  all 
the  arc-lamps. 

The  carbon  incandescent  filament  lamp  was  used  ex¬ 
tensively  until  1909,  when  the  tungsten  filament  lamp 
began  to  replace  it  very  rapidly.  However,  it  was  not 
until  1914,  when  the  gas-filled  tungsten  lamp  appeared, 
that  this  type  of  light-source  could  compete  with  arc- 
lamps  on  the  basis  of  efficiency.  The  helical  construc¬ 
tion  of  the  filament  made  it  possible  to  confine  the  fila¬ 
ment  of  a  high-intensity  tungsten  lamp  in  a  small  space 
and  for  the  first  time  a  high  degree  of  control  of  the 
light  of  street  lamps  was  possible.  Prismatic  “re¬ 
fractors”  were  designed,  somewhat  on  the  principle  of 


162 


ARTIFICIAL  LIGHT 


the  lighthouse  refractor,  so  that  the  light  would  be 
emitted  largely  just  below  the  horizontal.  This  type 
of  distribution  builds  up  the  illumination  at  distant 
points  between  successive  street  lamps,  which  is  very 
desirable  in  street-lighting.  The  incandescent  filament 
lamp  possesses  many  advantages  over  other  systems. 
It  is  efficient ;  capable  of  subdivision ;  operates  on  direct 
and  alternating  current ;  requires  little  attention ;  and 
is  capable  of  most  successful  use  with  light-controlling 
apparatus. 

According  to  the  reports  of  the  Department  of  Com¬ 
merce  the  number  of  electric  arc-lamps  for  street-light¬ 
ing  supplied  by  public  electric-light  plants  decreased 
from  348,643  in  1912  to  256,838  in  1917,  while  the  num¬ 
ber  of  electric  incandescent  filament  lamps  increased 
from  681,957  in  1912  to  1,389,382  in  1917. 

Street-lighting  is  not  only  a  reinforcement  for  the 
police  but  it  decreases  accidents  and  has  come  to  be 
looked  upon  as  an  advertising  medium.  In  the  down¬ 
town  districts  the  high-intensity  “white-way”  lighting 
is  festive.  The  ornamental  street  lamps  have  possi¬ 
bilities  in  making  the  streets  attractive  and  in  illumi¬ 
nating  the  buildings.  However,  it  is  to  be  hoped  that 
in  the  present  age  the  streets  of  cities  and  towns  will 
be  cleared  of  the  ragged  equipment  of  the  telephone 
and  lighting  companies.  These  may  be  placed  in  the 
alleys  or  underground,  leaving  the  streets  beautiful  by 
day  and  glorified  at  night  by  the  torches  of  advanced 
civilization. 


XIII 

LIGHTHOUSES 

At  the  present  time  thousands  of  lighthouses,  light¬ 
ships,  and  light-buoys  guide  the  navigator  along  the 
waterways  and  into  harbors  and  warn  him  of  danger¬ 
ous  shoals.  Many  wonderful  feats  of  engineering  are 
involved  in  their  construction  and  in  no  field  of  arti¬ 
ficial  lighting  has  more  ingenuity  been  displayed  in 
devising  powerful  beams  of  light.  Many  of  these 
beacons  of  safety  are  automatic  in  operation  and  re¬ 
quire  little  attention.  It  has  been  said  that  nothing 
indicates  the  liberality,  prosperity,  or  intelligence  of  a 
nation  more  clearly  than  the  facilities  which  it  affords 
for  the  safe  approach  of  the  mariner  to  its  shores. 
Surely  these  marine  lights  are  important  factors  in 
modern  navigation. 

The  first  “lighthouses”  were  beacon-fires  of  burning 
wood  maintained  by  priests  for  the  benefit  of  the  early 
commerce  in  the  eastern  part  of  the  Mediterranean 
Sea.  As  early  as  the  seventh  century  before  Christ 
these  beacon-fires  were  mentioned  in  writings.  In  the 
third  century  before  the  Christian  era  a  tower  said  to 
be  of  a  great  height  was  built  on  a  small  island  near 
Alexandria  during  the  reign  of  Ptolemy  II.  The  tower 
was  named  Pharos,  which  is  the  origin  of  the  term 
“pharology”  applied  to  the  science  of  lighthouse  con¬ 
struction.  Caesar,  who  visited  Alexandria  two  cen- 

163 


164 


ARTIFICIAL  LIGHT 


turies  later,  described  the  Pharos  as  a  4  Gower  of  great 
height,  of  wonderful  construction.  ’  ’  Fire  was  kept 
burning  in  it  night  and  day  and  Pliny  said  of  it,  4 4  Dur¬ 
ing  the  night  it  appears  as  bright  as  a  star,  and  during 
the  day  it  is  distinguished  by  the  smoke.’ ’  Appar¬ 
ently  this  tower  served  as  a  lighthouse  for  more  than 
a  thousand  years.  It  was  found  in  ruins  in  1349. 
Throughout  succeeding  centuries  many  towers  were 
built,  but  little  attention  was  given  to  the  development 
of  light-sources  and  optical  apparatus. 

The  first  lighthouse  in  the  United  States  and  perhaps 
on  the  Western  continents  was  the  Boston  Light,  which 
was  completed  in  1716.  A  few  days  after  it  was  put 
into  operation  a  news  item  in  a  Boston  paper  heralded 
the  noteworthy  event  as  follows: 

By  virtue  of  an  Act  of  Assembly  made  in  the  First 
Year  of  His  Majesty’s  Reign,  For  Building  and  Main¬ 
taining  a  Light  House  upon  the  Great  Brewster  (called 
Beacon-Island)  at  the  Entrance  of  the  Harbour  of 
Boston,  in  order  to  prevent  the  loss  of  the  Lives  and 
Estates  of  His  Majesty’s  Subjects;  the  said  Light 
House  has  been  built ;  and  on  Fryday  last  the  14th  Cur¬ 
rant  the  Light  was  kindled,  which  will  be  very  useful 
for  all  Vessels  going  out  and  coming  in  to  the  Harbour 
of  Boston,  or  any  other  Harbours  in  the  Massachusetts 
Bay,  for  which  all  Masters  shall  pay  to  the  Receiver 
of  Impost,  one  Penny  per  Ton  Inwards,  and  another 
Penny  Outwards,  except  Coasters,  who  are  to  pay  Two 
Shillings  each,  at  their  clearance  Out,  And  all  Fishing 
Vessels,  Wood  Sloops,  etc.  Five  Shillings  each  by  the 
Year. 

This  was  the  practical  result  of  a  petition  of  Boston 
merchants  made  three  years  before.  The  tower  was 


LIGHTHOUSES 


165 


built  of  stone,  at  a  cost  of  about  ten  thousand  dollars. 
Two  years  later  the  keeper  and  his  family  were 
drowned  and  the  catastrophe  so  affected  Benjamin 
Franklin,  a  boy  of  thirteen,  that  he  wrote  a  poem  con¬ 
cerning  it.  The  lighthouse  was  badly  damaged  during 
the  Revolution,  by  raiding-parties,  and  in  1776,  when 
the  British  fleet  left  the  harbor,  a  squad  of  sailors  blew 
it  up.  It  was  rebuilt  in  1783  and  has  since  been  in¬ 
creased  in  height. 

Apparently  oil-lamps  were  used  in  it  from  the  begin¬ 
ning,  notwithstanding  the  fact  that  candles  and  coal 
fires  served  for  years  in  many  lighthouses  of  Europe. 
In  1789  sixteen  lamps  were  used  and  in  1811  Argand 
lamps  and  reflectors  were  installed,  with  a  revolving 
mechanism.  It  now  ceased  to  be  a  fixed  light  and  the 
day  of  flashing  lights  had  arrived.  At  the  present 
time  the  Boston  Light  emits  a  beam  of  100,000  candle- 
power  directed  by  modern  lenses. 

When  the  United  States  Government  was  organized 
in  1789  there  were  ten  lighthouses  owned  by  the 
Colonies,  but  the  Boston  Light  was  in  operation  thirty 
years  before  the  others.  Sandy  Hook  Light,  New  York 
Harbor,  was  established  in  1764  and  its  original 
masonry  tower  is  still  standing  and  in  use.  It  is  the 
oldest  surviving  lighthouse  in  this  country.  It  was 
built  with  funds  raised  by  means  of  two  lotteries  au¬ 
thorized  by  the  New  York  Assembly.  A  few  days  after 
it  was  lighted  for  the  first  time  the  following  news  item 
appeared  in  a  New  York  paper: 

On  Monday  evening  last  the  New  York  Light-house 
erected  at  Sandy  Hook  was  lighted  for  the  first  time. 
The  House  is  of  an  Octagon  Figure,  having  eight  equal 


166 


ARTIFICIAL  LIGHT 


Sides ;  the  Diameter  at  the  Base  29  Feet ;  and  at  the  top 
of  the  Wall,  15  Feet.  The  Lanthorn  is  7  feet  high;  the 
Circumference  33  feet.  The  whole  Construction  of  the 
Lanthorn  is  Iron;  the  Top  covered  with  Copper. 
There  are  48  Oil  Blazes.  The  Building  from  the  Sur¬ 
face  is  Nine  Stories;  the  whole  from  Bottom  to  Top  is 
103  Feet. 

From  these  early  years  the  number  of  lighthouses 
has  steadily  grown,  until  now  the  United  States  main¬ 
tains  lights  along  50,000  miles  of  coast-line  and  river 
channels,  a  distance  equal  to  twice  the  circumference  of 
the  earth.  It  maintains  at  the  present  time  about 
15,000  aids  to  navigation  at  an  annual  cost  of  about 
$5,000,000.  In  1916  this  country  was  operating  1706 
major  lights,  53  light-ships,  and  512  light-buoys — a 
total  of  5323. 

The  earliest  lighthouses  were  equipped  with  braziers 
or  grates  in  which  coal  or  wood  was  burned.  These 
crude  light-sources  were  used  until  after  the  advent  of 
the  nineteenth  century  and  in  one  case  until  1846.  In 
the  famous  Eddystone  tower  off  Plymouth,  England, 
candles  were  used  for  the  first  time.  The  first  Eddy- 
stone  tower  was  completed  in  1698,  but  it  was  swept 
away  in  1703.  Another  was  built  and  destroyed  by 
fire  in  1755.  Smeaton  then  built  another  in  1759.  In¬ 
asmuch  as  Smeaton  is  credited  with  having  introduced 
the  use  of  candles,  this  must  have  occurred  in  the 
eighteenth  century;  still  it  appears  that,  as  we  have 
said,  the  Boston  Light,  built  in  1716,  used  oil-lamps 
from  its  beginning.  However,  Smeaton  installed 
twenty-four  candles  of  rather  large  size  each  credited 
with  an  intensity  of  2.8  candles.  The  total  luminous 


LIGHTHOUSES 


167 


intensity  of  the  light-source  in  this  tower  was  about  67 
candles.  Inasmuch  as  this  was  before  the  use  of  effi¬ 
cient  reflectors  and  lenses,  it  is  obvious  that  the  early 
lighthouses  were  rather  feeble  beacons. 

According  to  British  records,  oil-lamps  with  flat 
wicks  were  first  used  in  the  Liverpool  lighthouses  in 
1763.  The  Argand  lamp,  introduced  in  about  1784, 
became  widely  used.  The  better  combustion  obtained 
with  this  lamp  having  a  cylindrical  wick  and  a  glass 
chimney  greatly  increased  the  luminous  intensity  and 
general  satisfactoriness  of  the  oil-lamp.  Later  Lange 
added  an  improvement  by  providing  a  contraction  to¬ 
ward  the  upper  part  of  the  chimney.  Bumford  and 
also  Fresnel  devised  multiple-wick  burners,  thus  in¬ 
creasing  the  luminous  intensity.  In  these  early  lamps 
sperm-oil  and  colza-oil  were  burned  and  they  continued 
to  be  until  the  middle  of  the  nineteenth  century. 
Cocoanut-oil,  lard-oil,  and  olive-oil  have  also  been  used 
in  lighthouses. 

Naturally,  mineral  oil  was  introduced  as  soon  as  it 
was  available,  owing  to  its  lower  cost ;  but  it  was  not 
until  nearly  1870  that  a  satisfactory  mineral-oil  lamp 
was  in  operation  in  lighthouses.  Doty  is  credited  with 
the  invention  of  the  first  successful  multiple-widk 
lighthouse  lamp  using  mineral  oil,  and  his  lamp  and 
modifications  of  it  were  very  generally  used  until  the 
latter  part  of  the  nineteenth  century.  These  lamps  are 
of  two  types — one  in  which  oil  is  supplied  to  the  burner 
under  pressure  and  the  other  in  which  oil  is  maintained 
as  a  constant  level.  In  some  of  the  smallest  lamps  the 
ordinary  capillarity  of  the  wick  is  depended  on  to  sup¬ 
ply  oil  to  the  flame. 


168 


ARTIFICIAL  LIGHT 


Coal-gas  was  introduced  into  lighthouses  in  about 
the  middle  of  the  nineteenth  century.  Inasmuch  as 
the  gas-mantle  had  not  yet  appeared,  the  gas  was 
burned  in  jets.  Various  arrangements  of  the  jets,  such 
as  concentric  rings  forming  a  stepped  cone,  were  de¬ 
vised.  The  gas-mantle  was  a  great  boon  to  the  mariner 
as  well  as  to  civilized  beings  in  general.  It  greatly  in¬ 
creases  the  intensity  of  light  obtainable  from  a  given 
amount  of  fuel  and  it  is  a  fairly  compact  bright  source 
which  makes  it  possible  to  direct  the  light  to  some  de¬ 
gree  by  means  of  optical  systems.  Owing  to  the  elab¬ 
orate  apparatus  necessary  for  making  coal-gas,  several 
other  gases  have  been  more  desirable  fuels  for  light¬ 
house  lamps.  Various  simple  gas-generators  have 
been  devised.  Some  of  the  high-flash  mineral-oils  are 
vaporized  and  burned  under  a  mantle.  Acetylene, 
which  is  so  simply  made  by  means  of  calcium  carbide 
and  water,  has  been  a  great  factor  in  lighting  for  nav¬ 
igation.  By  the  latter  part  of  the  nineteenth  century 
lighthouses  employing  incandescent  gas-burners  were 
emitting  beams  of  light  having  luminous  intensities  as 
great  as  several  hundred  thousand  candles.  These 
special  gas-mantle  light-sources  have  brightness  as 
high  as  several  hundred  candles  per  square  inch. 

Electric  arc-lamps  were  first  introduced  into  light¬ 
house  service  in  about  1860,  but  these  lamps  cannot  be 
considered  to  have  been  really  practicable  until  about 
1875.  In  1883  the  British  lighthouse  authorities  car¬ 
ried  out  an  extensive  investigation  of  arc-lamps.  It 
was  found  that  the  whiter  light  from  these  lamps  suf¬ 
fered  a  greater  absorption  by  the  atmosphere  than  the 
yellower  light  from  oils,  but  the  much  greater  luminous 


LIGHTHOUSES 


169 


intensity  of  the  arc- lamp  more  than  compensated  for 
this  disadvantage.  The  final  result  of  the  investigation 
was  the  conclusion  that  for  ordinary  lighthouse  pur¬ 
poses  the  oil-  and  gas-lamps  were  more  suitable  and 
economical  than  arc-lamps ;  but  where  great  range  was 
desired,  the  latter  were  much  more  advantageous,  ow¬ 
ing  to  their  great  luminous  intensity.  Electric  incan¬ 
descent  filament  lamps  have  been  used  for  the  less  im¬ 
portant  lights,  and  recently  there  has  been  some  appli¬ 
cation  of  the  modern  high-efficiency  filament  lamps. 

Besides  the  high  towers  there  are  many  minor  bea¬ 
cons,  light-ships,  and  light-buoys  in  use.  Many  of  these 
are  untended  and  therefore  must  operate  automatically. 
The  light-ship  is  used  where  it  is  impracticable  or  too 
expensive  to  build  a  lighthouse.  Inasmuch  as  it  is 
anchored  in  fairly  deep  water,  it  is  safe  in  foggy 
weather  to  steer  almost  directly  toward  its  position  as 
indicated  by  the  fog-signal.  Light-ships  are  more  ex¬ 
pensive  to  maintain  than  lighthouses,  but  they  have  the 
advantages  of  smaller  cost  and  of  mobility;  for  some¬ 
times  it  may  be  desired  to  move  them.  The  first  light¬ 
ship  was  established  in  1732  near  the  mouth  of  the 
Thames,  and  the  first  in  this  country  was  anchored  in 
Chesapeake  Bay  near  Norfolk  in  1820.  The  early 
ships  had  no  mode  of  self-propulsion,  but  the  modern 
ones  are  being  provided  with  their  own  power.  Oil 
and  gas  have  been  used  as  fuel  for  the  light-sources  and 
in  1892  the  U.  S.  Lighthouse  Board  constructed  a  light¬ 
ship  with  a  powerful  electric  light.  Since  that  time 
several  have  been  equipped  with  electric  lights  sup¬ 
plied  by  electric  generators  and  batteries. 

Untended  lights  were  not  developed  until  about  1880, 


170 


ARTIFICIAL  LIGHT 


when  Pintsch  introduced  his  welded  buoys  filled  with 
compressed  gas  and  thereby  provided  a  complete 
lighting-plant.  With  improvements  in  lamps  and  con¬ 
trols  the  untended  light-buoys  became  a  success.  The 
lights  burn  for  several  months,  and  even  for  a  year  con¬ 
tinuously;  and  the  oil-gas  used  appears  to  be  very 
satisfactory.  Recently  some  experiments  have  been 
made  with  devices  which  would  be  actuated  by  sunlight 
in  such  a  manner  that  the  light  would  be  extinguished 
during  the  day  excepting  a  small  pilot-flame.  By  this 
means  a  longer  period  of  burning  without  attention 
may  be  obtained.  Electric  filament  lamps  supplied  by 
batteries  or  by  cables  from  the  shore  have  been  used, 
but  the  oil-gas  buoy  still  remains  in  favor.  Acetylene 
has  been  employed  as  a  fuel  for  light-buoys.  Auto¬ 
matic  generators  have  been  devised,  but  the  high-pres¬ 
sure  system  is  more  simple.  In  the  latter  case  purified 
acetylene  is  held  in  solution  under  high  pressure  in  a 
reservoir  containing  an  asbestos  composition  saturated 
with  acetone. 

The  light-sources  of  beacons  have  had  the  same  his¬ 
tory  as  those  of  other  navigation  lights.  Many  of 
these  are  automatic  in  operation,  sometimes  being  con¬ 
trolled  by  clockwork.  During  the  last  twenty  years 
the  gas-mantle  has  been  very  generally  applied  to 
beacon-lights.  In  the  latter  part  of  the  nineteenth  cen¬ 
tury  a  mineral-oil  lamp  was  devised  with  a  permanent 
wick  made  by  forming  upon  a  thick  wick  a  coating  of 
carbon.  The  operation  is  such  that  this  is  not  con¬ 
sumed  and  it  prevents  further  burning  of  the  wick. 

The  optical  apparatus  of  navigation  lights  has  under¬ 
gone  many  improvements  in  the  past  century.  The 


LIGHTHOUSES 


171 


early  lights  were  not  equipped  with  either  reflecting  or 
refracting  apparatus.  In  1824  Drummond  devised  a 
scheme  for  reflecting  light  in  order  that  a  distant  ob¬ 
server  might  make  a  reading  upon  the  point  where  the 
apparatus  was  being  operated  by  another  person.  He 
was  led  by  his  experiments  to  suggest  the  application 
of  mirrors  to  lighthouses.  His  device  was  essentially 
a  parabolic  mirror  similar  to  the  reflectors  now  widely 
used  in  automobile  head-lamps,  search-lights,  etc.  He 
employed  the  lime-light  as  a  source  of  light  and  was 
enthusiastic  over  the  results  obtained.  His  discussion 
published  in  1826  indicates  that  little  practical  work 
had  been  done  up  to  that  time  toward  obtaining  beams 
or  belts  of  light  by  means  of  optical  apparatus.  How¬ 
ever,  lighthouse  records  show  that  as  early  as  1763 
small  silvered  plane  glasses  were  set  in  plaster  of  Paris 
in  such  a  manner  as  to  form  a  partially  enveloping 
reflector.  Spherical  reflectors  were  introduced  in 
about  1780  and  parabolic  reflectors  about  ten  years 
later. 

All  the  earlier  lights  were  4 ‘ fixed,’ ’  but  as  it  is  de¬ 
sirable  that  the  mariner  be  able  to  distinguish  one  light 
from  another,  the  revolving  mechanism  evolved.  By 
its  agency  characteristic  flashes  are  obtained  and  from 
the  time  interval  the  light  is  recognized.  The  first  re¬ 
volving  mechanism  was  installed  in  1783.  The  early 
flashing  lights  were  obtained  by  means  of  revolving  re¬ 
flectors  which  gathered  the  light  and  directed  it  in  the 
form  of  a  beam  or  pencil.  The  type  of  parabolic  re¬ 
flector  now  in  use  does  not  differ  essentially  from  that 
of  an  automobile  head-lamp,  excepting  that  it  is  larger. 

Lenses  appear  to  have  been  introduced  in  the  latter 


172 


ARTIFICIAL  LIGHT 


part  of  the  nineteenth  century.  They  were  at  first 
ground  from  a  solid  piece  of  glass,  in  concentric  zones, 
in  order  to  reduce  the  thickness.  They  were  similar  in 
principle  to  some  of  the  tail-light  lenses  used  at  pres¬ 
ent  on  automobiles.  Later  the  lenses  were  built  up  by 
means  of  separate  annular  rings.  The  name  of  Fres¬ 
nel  is  permanently  associated  with  lighthouse  lenses 
because  in  1822  he  developed  an  elaborate  built-up  lens 
of  annular  rings.  The  centers  of  curvature  of  the  dif¬ 
ferent  rings  receded  from  the  axis  as  their  distance 
from  the  center  increased,  in  such  a  manner  as  to  over¬ 
come  a  serious  optical  defect  known  as  spherical  aber¬ 
ration.  Fresnel  devised  many  improvements  in  which 
he  used  refracting  and  reflecting  prisms  for  the  outer 
elements. 

The  optical  apparatus  of  lighthouses  usually  aims 
(1)  to  concentrate  the  rays  of  light  into  a  pencil  of 
light,  (2)  to  concentrate  them  into  a  belt  of  light,  or 
(3)  to  concentrate  the  rays  over  a  limited  azimuth.  In 
the  first  case  a  single  lens  or  a  parabolic  reflector  suf¬ 
fices,  but  in  the  second  case  a  cylindrical  lens  which 
condenses  the  light  vertically  into  a  horizontal  sheet  of 
light  is  essential.  The  third  case  is  a  combination  of 
the  first  two.  The  modern  lighthouse  lenses  are  very 
elaborate  in  construction,  being  built  up  by  means  of 
many  elements  into  several  sections.  For  example, 
the  central  section  may  consist  of  a  spherical  lens 
ground  with  annular  rings.  In  the  next  section  re¬ 
fracting  prisms  may  be  used  and  in  the  outer  section 
reflecting  glass  prisms  are  employed.  The  various  ele¬ 
ments  are  carefully  designed  according  to  the  laws  of 
geometrical  optics. 


LIGHTHOUSES 


173 


The  flashing  light  has  such  advantages  over  the  fixed 
that  it  is  generally  used  for  important  beacons.  A 
variety  of  methods  of  obtaining  intermittent  light  have 
been  employed,  but  they  are  not  of  particular  interest. 
Sometimes  the  lens  or  reflector  is  revolved  and  in  other 
types  an  opaque  screen  containing  slits  is  revolved. 
In  the  larger  lighthouses  the  optical  apparatus  and  its 
structure  sometimes  weigh  several  tons.  When  it  is 
necessary  to  revolve  apparatus  of  this  weight,  the 
whole  mechanism  is  floated  upon  mercury  contained  in 
a  cast-iron  vessel  of  suitable  size,  and  by  an  ingenious 
arrangement  only  a  small  portion  of  mercury  is  re¬ 
quired. 

The  characteristics  of  navigation  lights  are  varied 
considerably  in  order  to  enable  the  mariner  to  distin¬ 
guish  them  and  thereby  to  learn  exactly  where  he  is. 
The  fixed  light  is  liable  to  be  confused  with  others,  so 
it  has  now  become  a  minor  light.  Flashes  of  short 
duration  followed  by  longer  periods  of  darkness  are 
extensively  used.  The  mariner  by  timing  the  inter¬ 
vals  is  able  to  recognize  the  light.  This  method  is  ex¬ 
tended  to  groups  of  short  flashes  followed  by  longer 
intervals  of  darkness.  In  fact,  short  flashes  have  been 
employed  to  indicate  a  certain  number  so  that  a 
mariner  could  recognize  the  light  by  a  number  rather 
than  by  means  of  his  watch.  However,  a  time  element 
is  generally  used.  A  combination  of  fixed  light  upon 
which  is  superposed  a  flash  or  a  group  of  flashes  of 
white  or  of  colored  light  has  been  used,  but  it  is  in 
disrepute  as  being  unreliable.  A  type  known  as  “oc- 
culating  lights”  consists  of  a  fixed  light  which  is  momen¬ 
tarily  eclipsed,  but  the  duration  of  the  eclipse  is 


174 


ARTIFICIAL  LIGHT 


usually  less  than  that  of  the  light.  Obviously,  groups 
of  eclipses  may  be  used.  Sometimes  lights  of  differ¬ 
ent  colors  are  alternated  without  any  dark  intervals. 
The  colored  ones  used  are  generally  red  and  green,  but 
these  are  short-range  lights  at  best.  Colored  sectors 
are  sometimes  used  over  portions  of  the  field,  in  order 
to  indicate  dangers,  and  white  light  shows  in  the  fair¬ 
way.  These  are  usually  fixed  lights  for  marking  the 
channel. 

The  distance  at  which  a  light  may  be  seen  at  sea 
depends  upon  its  luminous  intensity,  upon  its  color  or 
spectral  composition,  upon  its  height  and  that  of  the 
observer ’s  eyes  above  the  sea-level,  and  upon  the  atmos¬ 
pheric  conditions.  Assuming  a  perfectly  clear  atmos¬ 
phere,  the  visibility  of  a  light-source  apparently  de¬ 
pends  directly  upon  its  candle-power.  The  atmosphere 
ordinarily  absorbs  the  red,  orange,  and  yellow  rays 
less  than  the  green,  blue,  and  violet  rays.  This  is 
demonstrated  by  the  setting  sun,  which  as  it  approaches 
closer  to  the  horizon  changes  from  yellow  to  orange 
and  finally  to  red  as  the  amount  of  atmosphere  between 
it  and  the  eye  increases.  For  this  reason  a  red  light 
would  have  a  greater  range  than  a  blue  light  of  the 
same  luminous  intensity. 

Under  ordinary  atmospheric  conditions  the  range  of 
the  more  powerful  light-sources  used  in  lighthouses  is 
greater  than  the  range  as  limited  by  the  curvature  of 
the  earth.  For  the  uncolored  illuminants  the  range  in 
nautical  miles  appears  to  be  at  least  equal  to  the  square 
root  of  the  candle-power.  A  real  practical  limitation 
which  still  exists  is  the  curvature  of  the  earth,  and  the 
distance  an  object  may  be  seen  by  the  eye  at  sea-level 


LIGHTHOUSES  175 


depends  upon  the  height  of  the  object.  The  relation 
is  approximately  expressed  thus, — 


Range  in  nautical  miles  —  —  V Height  of  object  in  feet 
F or  example,  the  top  of  a  tower  100  feet  high  is  visible 

g  _  gQ 

to  an  eye  at  sea-level  a  distance  of  —  \/100=— = 

11.43  miles.  Now  if  the  eye  is  49  feet  above  sea-level, 
a  similar  computation  will  show  how  far  away  it  may 
be  seen  by  the  original  eye  at  sea-level.  This  is 

g  _ 

—  \/49  =  8  miles.  Hence  an  eye  49  feet  above  sea- 


level  will  be  able  to  see  the  top  of  the  100-foot  tower  at 
a  distance  of  11.43  +  8  or  19.43  nautical  miles.  Under 
these  conditions  an  imaginary  line  drawn  from  the  top 
of  the  tower  to  the  eye  will  be  just  tangent  to  the 
spherical  surface  of  the  sea  at  a  distance  of  8  miles 
from  the  eye  and  11.43  miles  from  the  tower. 

The  luminous  intensity  of  a  light-source  or  of  the 
beam  of  light  is  directly  responsible  for  the  range. 
The  luminous  intensity  of  the  early  beacon-fires  and 
oil-lamps  was  equivalent  to  a  few  candles.  The  im¬ 
provements  in  light-sources  and  also  in  reflecting  and 
refracting  optical  systems  have  steadily  increased  the 
candle-power  of  the  beams,  until  to-day  the  beams  from 
gas-lamps  have  intensities  as  high  as  several  hundred 
thousand  candle-power.  The  beams  sent  forth  by 
modern  lighthouses  equipped  with  electric  lamps  and 
enormous  light-gathering  devices  are  rated  in  millions 
of  candle-power.  In  fact,  Navesink  Light  at  the  en¬ 
trance  of  New  York  Bay  is  rated  as  high  as  60,000,000 
candle-power. 


176 


ARTIFICIAL  LIGHT 


Of  course,  liglit-production  has  increased  enormously 
in  efficiency  in  the  past  century,  but  without  optical 
devices  for  gathering  the  light,  the  enormous  beam  in¬ 
tensity  would  not  be  obtained.  For  example,  consider 
a  small  source  of  light  possessing  a  luminous  intensity 
of  one  candle  in  all  directions.  If  all  this  light  which 
is  emitted  in  all  directions  is  gathered  and  sent  forth 
in  a  beam  of  small  angle,  say  one  thousandth  of  the 
total  angle  surrounding  a  point,  the  intensity  of  this 
beam  would  be  1000  candles.  It  is  in  this  manner  that 
the  enormous  beam  intensities  are  built  up. 

There  is  an  interesting  point  pertaining  to  short 
flashes  of  light.  To  the  dark-adapted  eye  a  brief  flash 
is  registered  as  of  considerably  higher  intensit}^  than 
if  the  light  remained  constant.  In  other  words,  the 
lookout  on  a  vessel  is  adapted  to  darkness  and  a  flash 
from  a  beam  of  light  is  much  brighter  than  if  the  same 
beam  were  shining  steadily.  This  is  a  physiological 
phenomenon  which  operates  in  favor  of  the  flashing 
light. 

Doubtless,  the  reader  has  noted  that  reliability,  sim¬ 
plicity,  and  low  cost  of  operation  are  the  primary  con¬ 
siderations  for  light-sources  used  as  aids  to  navigation. 
This  accounts  for  the  continued  use  of  oil  and  gas. 
From  an  optical  standpoint  the  electric  arc-lamps  and 
concentrated-filament  lamps  are  usually  superior  to  the 
earlier  sources  of  light,  but  the  complexity  of  a  plant 
for  generating  electricity  is  usually  a  disadvantage  in 
isolated  places.  The  larger  light-ships  are  now  using 
electricity  generated  by  apparatus  installed  in  the  ves¬ 
sels.  There  seems  to  be  a  tendency  toward  the  use 


A.  A  COMPLETED  LIGHTHOUSE  LENS 
B.  TORRO  POINT  LIGHTHOUSE,  PANAMA  CANAL 


AMERICAN  SEARCH-LIGHT  POSITION  ON  WESTERN  FRONT  IN  1919 


AMERICAN  STANDARD  FIELD  SEARCH-LIGHT  AND  POWER  UNIT 


LIGHTHOUSES  177 

of  more  buoys  and  fewer  lighthouses,  but  the  beam- 
intensities  of  the  latter  are  increasing. 

In  the  hundred  years  since  the  Boston  Light  was 
built  the  same  great  changes  wrought  by  the  develop¬ 
ment  of  artificial  light  in  other  activities  of  civilization 
have  appeared  in  the  beacons  of  the  mariner.  The 
development  of  these  aids  to  navigation  has  been  won¬ 
derful,  but  it  must  go  on  and  on.  The  surface  of  the 
earth  comprises  51,886,000  square  statute  miles  of  land 
and  145,054,000  square  miles  of  water.  Three  fourths 
of  the  earth’s  surface  is  water  and  the  oceans  will  al¬ 
ways  be  highways  of  world  commerce.  All  the  dan¬ 
gers  cannot  be  overcome,  but  human  ingenuity  is  Capa¬ 
ble  of  great  achievements.  Wreckage  will  appear 
along  the  shore-lines  despite  the  lights,  but  the  harvest 
of  the  shoals  has  been  much  reduced  since  the  time 
described  by  Robert  Louis  Stevenson,  when  the  coast 
people  in  the  Orkneys  looked  upon  wrecks  as  a  source 
of  gain.  He  states : 

It  had  become  proverbial  with  some  of  the  inhabi¬ 
tants  to  observe  that  “if  wrecks  were  to  happen,  they 
might  as  well  be  sent  to  the  poor  island  of  Sanday  as 
anywhere  else.”  On  this  and  the  neighboring  island, 
the  inhabitants  have  certainly  had  their  share  of 
wrecked  goods.  On  complaining  to  one  of  the  pilots  of 
the  badness  of  his  boat’s  sails,  he  replied  with  some  de¬ 
gree  of  pleasantry,  “Had  it  been  His  [God’s]  will  that 
you  come  na  here  wi  these  lights,  we  might  a’  had  better 
sails  to  our  boats  and  more  o’  other  things.” 

In  the  leasing  of  farms,  a  location  with  a  greater 
probability  of  shipwreck  on  the  shore  brought  a  much 
higher  rent. 


XIV 

ARTIFICIAL  LIGHT  IN  WARFARE 


When  the  recent  war  broke  out  science  responded  to 
the  call  and  under  the  stress  of  feverish  necessity  com¬ 
pressed  the  normal  development  of  a  half-century  into 
a  few  years.  The  airplane,  in  1914  a  doubtful  play¬ 
thing  of  daredevils,  emerged  from  the  war  a  perfected 
thing  of  the  air.  Lighting  did  not  have  the  glamor  of 
flying  or  the  novelty  of  chemical  warfare,  but  it  pro¬ 
gressed  greatly  in  certain  directions  and  served  well. 
While  artificial  lighting  conducted  its  unheralded  of¬ 
fensive  by  increasing  production  in  the  supporting  in¬ 
dustries  and  helped  to  maintain  liaison  with  the  front¬ 
line  trenches  by  lending  eyes  to  transportation,  it  was 
also  doing  its  part  at  the  battle  front.  Huge  search¬ 
lights  revealed  the  submarine  and  the  aerial  bomber; 
flares  exposed  the  manoeuvers  of  the  enemy;  rockets 
brought  aid  to  beleaguered  vessels  and  troops;  pistol 
lights  fired  by  the  aerial  observer  directed  artillery 
fire;  and  many  other  devices  of  artificial  light  were 
in  the  frav.  Many  improvements  were  made  in  search¬ 
lights  and  in  signaling  devices  and  the  elements  of  the 
festive  fireworks  of  past  ages  were  improved  and  de¬ 
veloped  for  the  needs  of  modern  warfare. 

Night  after  night  along  the  battle  front  flares  were 
sent  up  to  reveal  patrols  and  any  other  enemy  activity. 

On  the  slightest  suspicion  great  swarms  of  these  bril- 

178 


ARTIFICIAL  LIGHT  IN  WARFARE  179 


liant  lights  would  burst  forth  as  though  flocks  of  huge 
fireflies  had  been  disturbed.  They  were  even  used  as 
light  barrages,  for  movements  could  be  executed  in 
comparative  safety  when  a  large  number  of  these  lights 
lay  before  the  enemy’s  trenches  sputtering  their  bril¬ 
liant  light.  The  airman  dropped  flares  to  illuminate 
his  target  or  his  landing  field.  The  torches  of  past 
parades  aided  the  soldier  in  his  night  operations  and 
rockets  sent  skyward  radiated  their  messages  to  head¬ 
quarters  in  the  rear.  The  star-shell  had  the  same  mis¬ 
sions  as  other  flares,  but  it  was  projected  by  a  charge 
of  powder  from  a  gun.  These  and  many  modifications 
represent  the  useful  applications  of  what  formerly 
were  mere  “ fireworks.”  Those  which  are  primarily 
signaling  devices  are  discussed  in  another  chapter,  but 
the  others  will  be  described  sufficiently  to  indicate  the 
place  which  artificial  light  played  in  certain  phases  of 
warfare. 

The  illuminating  compounds  used  in  these  devices 
are  not  particularly  new,  consisting  essentially  of  a 
combustible  powder  and  chemical  salts  which  make  the 
flame  luminous  and  give  it  color  when  desired.  Among 
the  ingredients  are  barium  nitrate,  potassium  perchlo¬ 
rate,  powdered  aluminum,  powdered  magnesium,  po¬ 
tassium  nitrate,  and  sulphur.  One  of  the  simplest  mix¬ 
tures  used  by  the  English  is, 


Barium  nitrate .  37  per  cent. 

Powdered  magnesium .  34  per  cent. 

Potassium  nitrate  .  29  per  cent. 


The  magnesium  is  coated  with  hot  wax  or  paraffin, 
which  not  only  acts  as  a  binder  for  the  mixture  when 


180 


ARTIFICIAL  LIGHT 


it  is  pressed  into  its  container  but  also  serves  to  pre¬ 
vent  oxidation  of  the  magnesium  when  the  shells  are 
stored.  The  barium  and  potassium  nitrates  supply  the 
oxygen  to  the  magnesium,  which  burns  with  a  brilliant 
white  flame.  The  potassium  nitrate  takes  fire  more 
readily  than  the  barium  nitrate,  but  it  is  more  ex¬ 
pensive  than  the  latter. 

Owing  to  the  cost  of  magnesium,  powdered  aluminum 
has  been  used  to  some  extent  as  a  substitute.  Alumi¬ 
num  does  not  have  the  illuminating  value  of  magnesium 
and  it  is  more  difficult  to  ignite,  but  it  is  a  good  sub¬ 
stitute  in  case  of  necessity.  An  English  mixture  con¬ 
taining  these  elements  is, 

Barium  nitrate  .  58  per  cent. 

Magnesium  .  29  per  cent. 

Aluminum .  13  per  cent. 

Mixtures  which  are  slow  to  ignite  must  be  supple¬ 
mented  by  a  primary  mixture  which  is  readily  ignited. 
For  obtaining  colored  lights  it  is  only  necessary  to 
add  chemicals  which  will  give  the  desired  color.  The 
mixtures  can  be  proportioned  by  means  of  purely  theo¬ 
retical  considerations ;  that  is,  just  enough  oxygen  can 
be  present  to  burn  the  fuel  completely.  However,  usu¬ 
ally  more  oxygen  is  supplied  than  called  for  by  theory. 

The  illuminating  shell  is  perhaps  the  most  useful  of 
these  devices  to  the  soldier.  It  has  been  constructed 
with  and  without  parachutes,  the  former  providing  an 
intense  light  for  a  brief  period  because  it  falls  rapidly. 
These  shells  of  the  larger  calibers  are  equipped  with 
time-fuses  and  are  generally  rather  elaborate  in  con¬ 
struction.  The  shell  is  of  steel,  and  has  a  time-fuse 


ARTIFICIAL  LIGHT  IN  WARFARE  181 


at  the  tip.  This  fuse  ignites  a  charge  of  black  powder 
in  the  nose  of  the  shell  and  this  explosion  ejects  the 
star-shell  out  of  the  rear  of  the  steel  casing.  At  the 
same  time  the  black  powder  ignites  the  priming  mixture 
next  to  it,  which  in  turn  ignites  the  slow-burning  illumi¬ 
nating  compound.  The  star-shell  has  a  large  para¬ 
chute  of  strong  material  folded  in  the  rear  of  the  cas¬ 
ing  and  the  cardboard  tube  containing  the  illuminating 
mixture  is  attached  to  it.  The  time  of  burning  varies, 
but  is  ordinarily  less  than  a  minute.  Certain  struc¬ 
tural  details  must  be  such  as  to  endure  the  stresses  of 
a  high  muzzle  velocity.  Furthermore,  a  velocity  of 
perhaps  1000  feet  per  second  still  obtains  when  the 
star-shell  with  its  parachute  is  ejected  at  the  desired 
point  in  the  air. 

The  non-parachute  illuminating  shell  is  designed  to 
give  an  intense  light  for  a  brief  interval  and  is  espe¬ 
cially  applicable  to  defense  against  air  raids.  Such  a 
light  aims  to  reveal  the  aircraft  in  order  that  the  gun¬ 
ners  may  tire  at  it  effectively.  These  shells  are  fitted 
with  time-fuses  which  fire  the  charge  of  black  powder 
at  the  desired  interval  after  the  discharge  of  the  shell 
from  the  gun.  The  contents  of  the  shell  are  thereby 
ejected  and  ignited.  The  container  for  the  illuminat¬ 
ing  material  is  so  designed  that  there  is  rapid  combus¬ 
tion  and  consequently  a  brilliant  light  for  about  ten 
seconds.  The  enemy  airman  in  this  short  time  is  un¬ 
able  to  obtain  any  valuable  knowledge  pertaining  to  the 
earth  below  and  furthermore  he  is  likely  to  be  tem¬ 
porarily  blinded  by  the  brilliant  light  if  it  is  near 
him. 

The  rifle-light  which  resembles  an  ordinary  rocket, 


182 


ARTIFICIAL  LIGHT 


is  fired  from  a  rifle  and  is  designed  for  short-range  use. 
It  consists  of  a  steel  cylindrical  shell  a  few  inches  long 
fastened  to  a  steel  rod.  A  parachute  is  attached  to  the 
cardboard  container  in  which  the  illuminating  mixture 
is  packed  and  the  whole  is  stowed  away  in  the  steel 
shell.  Shore  delay-fuses  are  used  for  starting  the 
usual  cycle  of  events  after  the  rifle-light  has  been  fired 
from  the  gun.  The  steel  rod  is  injected  into  the  barrel 
of  a  rifle  and  a  blank  cartridge  is  used  for  ejecting  this 
rocket-like  apparatus.  Owing  to  inertia  the  firing-pin 
in  the  shell  operates  and  the  short  delay-fuse  is  thus 
fired  automatically  an  instant  after  the  trigger  of  the 
rifle  is  pulled. 

Illuminating  4  4  bombs  ”  of  the  same  general  principles 
are  used  by  airmen  in  search  of  a  landing  for  himself 
or  for  a  destructive  bomb ;  in  signaling  to  a  gunner,  and 
in  many  other  ways.  They  are  simple  in  construction 
because  they  need  not  withstand  the  stresses  of  being 
fired  from  a  gun;  they  are  merely  dropped  from  the 
aircraft.  The  mechanism  of  ignition  and  the  cycle  of 
events  which  follow  are  similar  to  those  of  other  illu¬ 
minating  shells. 

The  value  of  such  artificial-lighting  devices  depends 
both  upon  luminous  intensity  and  time  of  burning.  Al¬ 
though  long-burning  is  not  generally  required  in  war¬ 
fare,  it  is  obvious  that  more  than  a  momentary  light 
is  usually  needed.  In  general,  high  candle-power  and 
long-burning  are  opposed  to  each  other,  so  that  the 
most  intense  lights  of  this  character  usually  are  of 
short  duration.  Typical  performances  of  two  flares  of 
the  same  composition  are  as  follows: 


ARTIFICIAL  LIGHT  IN  WARFARE  183 


Flare  No.  1  Flare  No.  2 

Average  candle-power  .  270,000  95,000 

Seconds  of  burning .  10  35 

Candle-seconds  .  2,700,000  3,325,000 

Cubic  inches  of  compound  ...  6  7 

Candle-seconds  per  cubic  inch  450,000  475,000 

Candle-hours  per  cubic  inch  . .  125  132 

The  illuminating  compound  was  the  same  in  these  two 
flares,  which  differed  only  in  the  time  allowed  for  burn¬ 
ing.  Of  course,  the  measurements  of  the  luminous  in¬ 
tensity  of  such  flares  is  difficult  because  of  the  fluctua¬ 
tions,  but  within  the  errors  of  the  measurements  it  is 
seen  that  the  illuminating  power  of  the  compound  is 
about  the  same  regardless  of  the  time  of  burning.  The 
light-source  in  the  case  of  burning  powders  is  really  a 
flame,  and  inasmuch  as  the  burning  end  hangs  down¬ 
ward,  more  light  is  emitted  in  the  lower  hemisphere 
than  in  the  upper.  The  candle-power  of  the  largest 
flares  equals  the  combined  luminous  intensities  of  200 
street  arc-lamps  or  of  10,000  ordinary  40-watt  tung¬ 
sten  lamps  such  as  are  used  in  residence  lighting. 

It  is  interesting  to  note  the  candle-hours  obtained 
per  cubic  inch  of  compound  and  to  find  that  the  cost  of 
this  light  is  less  than  that  of  candles  at  the  present 
time  and  only  five  or  ten  times  greater  than  that  of 
modern  electric  lighting. 

Illuminating  shells  in  use  during  the  recent  war  were 
designed  for  muzzle  velocities  as  high  as  2700  feet  per 
second  and  were  gaged  to  ignite  at  any  distance  from  a 
quarter  of  a  mile  to  several  miles.  The  maximum 
range  of  illuminating  shells  fired  from  rifles  was  about 


184 


ARTIFICIAL  LIGHT 


200  yards;  for  trench  mortars  about  one  mile;  and 
from  field  and  naval  guns  about  four  miles. 

The  search-light  has  long  been  a  valuable  aid  in  war¬ 
fare  and  during  the  recent  conflict  considerable  atten¬ 
tion  was  given  to  its  development  and  application.  It 
is  used  chiefly  for  detecting  and  illuminating  distant 
targets,  but  this  covers  a  wide  range  of  conditions  and 
requirements.  In  order  that  a  search-light  may  be  ef¬ 
fective  at  a  great  distance,  as  much  as  possible  of  the 
light  emitted  by  a  source  is  directed  into  a  beam  of  light 
of  as  nearly  parallel  rays  as  can  be  obtained.  Re¬ 
flectors  are  usually  employed  in  military  search-lights, 
and  in  order  that  the  beam  may  be  as  nearly  parallel 
(minimum  divergence)  as  possible,  the  light  must  be 
emitted  by  the  smallest  source  compatible  with  high  in¬ 
tensity.  This  source  is  placed  at  the  proper  point  in 
respect  to  a  large  parabolic  reflecter  which  renders  the 
rays  parallel  or  nearly  so. 

Ever  since  its  advent  the  electric  arc  has  been  em¬ 
ployed  in  large  search-lights,  with  which  the  army  and 
the  navy  were  supplied ;  however,  the  greatest  improve¬ 
ments  have  been  made  under  the  stress  of  war.  The 
science  of  aeronautics  advanced  so  rapidly  during  the 
recent  war  that  the  necessity  for  powerful  search¬ 
lights  was  greatly  augmented  and  as  the  conflict  pro¬ 
gressed  the  enemy  airmen  came  to  look  upon  the  newly 
developed  ones  with  considerable  concern.  The 
rapidly  moving  aircraft  and  its  high  altitude  brought 
new  factors  into  the  design  of  these  lights.  It  now 
became  necessary  to  have  the  most  intense  beam  and  to 
be  able  to  sweep  the  heavens  with  it  by  means  of  deli¬ 
cate  controlling  apparatus,  for  the  targets  were  some- 


ARTIFICIAL  LIGHT  IN  WARFARE  185 


times  minute  specks  moving  at  high  speed  at  altitudes 
as  high  as  five  miles.  Furthermore,  owing  to  the 
shifting  battle  areas,  mobile  apparatus  was  necessary. 

The  control  of  light  by  means  of  reflectors  has  been 
studied  for  centuries,  but  until  the  advent  of  the  electric 
arc  the  light-sources  were  of  such  large  areas  that  ef¬ 
fective  control  was  impossible.  Optical  devices  gener¬ 
ally  are  considered  in  connection  with  4 ‘ point  sources,’ ’ 
but  inasmuch  as  no  light  can  be  obtained  from  a  point, 
a  source  of  small  dimensions  and  of  high  brightness 
is  the  most  effective  compromise.  Parabolic  mirrors 
were  in  use  in  the  eighteenth  century  and  their  proper¬ 
ties  were  known  long  before  the  first  search-light 
worthy  of  the  name  was  made  in  1825  by  Drummond, 
who  used  as  a  source  of  light  a  piece  of  lime  heated  to 
incandescence  in  h  blast  flame.  He  finally  developed 
the  “lime-light”  by  directing  an  oxyhydrogen  flame 
upon  a  piece  of  lime  and  this  device  was  adapted  to 
search-lights  and  to  indoor  projection.  It  is  said  that 
the  first  search-light  to  be  used  in  warfare  was  a  Drum¬ 
mond  lime-light  which  played  a  part  in  the  attack  on 
Fort  Wagner  at  Charleston  in  1863. 

In  1848  the  first  electric  arc  lamp  used  for  general 
lighting  was  installed  in  Paris.  It  was  supplied  with 
current  by  a  large  voltaic  cell,  but  the  success  of  the 
electric  arc  was  obliged  to  await  the  development  of  a 
more  satisfactory  source  of  electricity.  A  score  oi 
years  was  destined  to  elapse,  after  the  public  was 
amazed  by  the  first  demonstration,  before  a  suitable 
electric  dynamo  was  invented.  With  the  advent  of  the 
dynamo,  the  electric  arc  was  rapidly  developed  and 
thus  there  became  available  a  concentrated  light-source 


186 


ARTIFICIAL  LIGHT 


of  high  intensity  and  great  brilliancy.  Gradually  the 
size  was  increased,  until  at  the  present  time  mirrors  as 
large  as  seven  feet  in  diameter  and  electric  currents 
as  great  as  several  hundred  amperes  are  employed. 
The  beam  intensities  of  the  most  powerful  search-lights 
are  now  as  great  as  several  hundred  million  candles. 

The  most  notable  advance  in  the  design  of  arc  search¬ 
lights  was  achieved  in  recent  years  by  Beck,  who  de¬ 
veloped  an  intensive  flame  carbon-arc.  His  chief  ob¬ 
ject  was  to  send  a  much  greater  current  through  the  arc 
than  had  been  done  previously  without  increasing  the 
size  of  the  carbons  and  the  unsteadiness  of  the  arc. 
In  the  ordinary  arc  excessive  current  causes  the  car¬ 
bons  to  disintegrate  rapidly  unless  they  are  of  large 
diameter.  Beck  directed  a  stream  of  alcohol  vapor  at 
the  arc  and  they  were  kept  from  oxidizing.  He  thus 
achieved  a  high  current-density  and  much  greater  beam 
intensities.  He  also  used  cored  carbons  containing 
certain  metallic  salts  which  added  to  the  luminous  in¬ 
tensity,  and  by  rotation  of  the  positive  carbon  so  that 
the  crater  was  kept  in  a  constant  position,  greater 
steadiness  and  uniformity  were  obtained.  Tests  show 
that,  in  addition  to  its  higher  luminous  efficiency,  an 
arc  of  this  character  directs  a  greater  percentage  of  the 
light  into  the  effective  angle  of  the  mirror.  The  small 
source  results  in  a  beam  of  small  divergence ;  in  other 
words,  the  beam  differs  from  a  cylinder  by  only  one  or 
two  degrees.  If  the  beam  consisted  entirely  of  parallel 
rays  and  if  there  were  no  loss  of  light  in  the  atmos¬ 
phere  by  scattering  or  by  absorption,  the  beam  in¬ 
tensity  would  be  the  same  throughout  its  entire  length. 
However,  both  divergence  and  atmospheric  losses  tend 


ARTIFICIAL  LIGHT  IN  WARFARE  187 


to  reduce  the  intensity  of  the  beam  as  the  distance  from 
the  search-light  increases. 

Inasmuch  as  the  intensity  of  the  beam  depends  upon 
the  actual  brightness  of  the  light-source,  the  brightness 
of  a  few  modern  light-sources  are  of  interest.  These 
are  expressed  in  candles  per  square  inch  of  projected 
area;  that  is,  if  a  small  hole  in  a  sheet  of  metal  is 
placed  next  to  the  light-source  and  the  intensity  of  the 
light  passing  through  this  hole  is  measured,  the  bright¬ 
ness  of  the  hole  is  easily  determined  in  candles  per 
square  inch. 

Brightness  of  Light-Sources  in  Candles  per  Square  Inch 


Kerosene  flame .  5  to  10 

Acetylene  .  30  to  60 

Gas-mantle  .  30  to  500 

Tungsten  filament  (vacuum)  lamp  ...  750  to  1,200 

Tungsten  filament  (gas-filled)  lamp  ..  3,500  to  18,000 

Magnetite  arc  .  4,000  to  6,000 

Carbon  arc  for  search-lights .  80,000  to  90,000 

Flame  arc  for  search-lights .  250,000  to  350,000 

Sun  (computed  mean)  .  about  1,000,000 


As  the  reflector  of  a  search-light  is  an  exceedingly 
important  factor  in  obtaining  high  beam-intensities, 
considerable  attention  has  been  given  to  it  since  the 
practicable  electric  arc  appeared.  The  parabolic  mir¬ 
ror  has  the  property  of  rendering  parallel,  or  nearly 
so,  the  rays  from  a  light-source  placed  at  its  focus. 
If  the  mirror  subtends  a  large  angle  at  the  light-source, 
a  greater  amount  of  light  is  intercepted  and  rendered 
parallel  than  in  the  case  of  smaller  subtended  angles ; 
hence,  mirrors  are  large  and  of  as  short  focus  as  prac- 


188 


ARTIFICIAL  LIGHT 


ticable.  Search-light  projectors  direct  from  30  to  60 
per  cent,  of  the  available  light  into  the  beam,  but  with 
lens  systems  the  effective  angle  is  so  small  that  a  much 
smaller  percentage  is  delivered  in  the  beam.  Mangin 
in  1874  made  a  reflector  of  glass  in  which  both  outer 
and  inner  surfaces  were  spherical  but  of  different  radii 
of  curvature,  so  that  the  reflector  was  thicker  in  the 
middle.  This  device  was  “ silvered’ ’  on  the  outside 
and  the  refraction  in  the  glass,  as  the  light  passed 
through  it  to  the  mirror  and  back  again,  corrected  the 
spherical  aberration  of  the  mirrored  surface.  These 
have  been  extensively  used.  Many  combinations  of 
curved  surfaces  have  been  developed  for  special  pro¬ 
jection  purposes,  but  the  parabolic  mirror  is  still  in 
favor  for  powerful  search-lights.  The  tip  of  the  posi¬ 
tive  carbon  is  placed  at  its  focus  and  the  effective  angle 
in  which  light  is  intercepted  by  the  mirror  is  generally 
about  125  degrees.  Within  this  angle  is  included  a 
large  portion  of  the  light  emitted  by  the  light-source 
in  the  case  of  direct-current  arcs.  If  this  angle  is  in¬ 
creased  for  a  mirror  of  a  given  diameter  by  decreasing 
its  focal  length,  the  divergence  of  the  beam  is  increased 
and  the  beam-intensity  is  diminished.  This  is  due  to 
the  fact  that  the  light-source  now  becomes  apparently 
larger ;  that  is,  being  of  a  given  size  it  now  subtends  a 
larger  angle  at  the  reflector  and  departs  more  from  the 
theoretical  point. 

When  the  recent  war  began  the  search-lights  avail¬ 
able  were  intended  generally  for  fixed  installations. 
These  were  “barrel”  lights  with  reflectors  several  feet 
in  diameter,  the  whole  output  sometimes  weighing  as 
much  as  several  tons.  Shortly  after  the  entrance  of 


ARTIFICIAL  LIGHT  IN  WARFARE  189 


this  country  into  the  war,  a  mobile  “barrel”  search¬ 
light  five  feet  in  diameter  was  produced,  which,  com¬ 
plete  with  carriage,  weighed  only  1800  pounds.  Later 
there  were  further  improvements.  An  example  of  the 
impetus  which  the  stress  of  war  gives  to  technical  ac¬ 
complishments  is  found  in  the  development  of  a  par¬ 
ticular  mobile  searchlight.  Two  months  after  the  War 
Department  submitted  the  problems  of  design  to  cer¬ 
tain  large  industrial  establishments  a  new  60-inch 
search-light  was  placed  in  production.  It  weighed  one 
fifth  as  much  as  the  previous  standard;  it  had  one 
twentieth  the  bulk;  it  was  much  simpler;  it  could  be 
built  in  one  fourth  the  time ;  and  it  cost  half  as  much. 
Remote  control  of  the  apparatus  has  been  highly  de¬ 
veloped  in  order  that  the  operator  may  be  at  a  distance 
from  the  scattered  light  near  the  unit.  If  he  is  near 
the  search-light,  this  veil  of  diffused  light  very  seri¬ 
ously  interferes  with  his  vision. 

Mobile  power-units  were  necessary  and  the  types  de¬ 
veloped  used  the  automobile  engine  as  the  prime  mover. 
In  one  the  generator  is  located  in  front  of  the  engine 
and  supported  beyond  the  automobile  chassis.  In  an¬ 
other  type  the  generator  is  located  between  the  auto¬ 
mobile  transmission  and  the  differential.  A  standard 
clutch  and  gear-shift  lever  is  employed  to  connect  the 
engine  either  with  the  generator  or  with  the  propeller 
shaft  of  the  truck.  The  first  type  included  a  115-volt, 
15-kilowatt  generator,  a  36-inch  wheel  barrel  search¬ 
light,  and  500  feet  of  wire  cable.  The  second  type  in¬ 
cluded  a  105-volt,  20-kilowatt  generator,  a  60-inch  open 
searchlight,  and  600  feet  of  cable.  This  type  has  been 
extended  in  magnitude  to  include  a  50-kilowatt  gen- 


190 


ARTIFICIAL  LIGHT 


erator.  When  these  units  are  moved,  the  search-light 
and  its  carriage  are  loaded  upon  the  rear  of  the  mobile 
generating  equipment.  An  idea  of  the  intensities  ob¬ 
tainable  with  the  largest  apparatus  is  gained  from  illu¬ 
mination  produced  at  a  given  distance.  For  example, 
the  15-kilowatt  search-light  with  highly  concentrated 
beam,  produced  an  illumination  at  930  feet  of  280  foot- 
candles.  At  this  point  this  is  the  equivalent  of  the  illu¬ 
mination  produced  by  a  source  having  a  luminous  in¬ 
tensity  of  nearly  250,000,000  candles. 

Of  course,  the  range  at  which  search-lights  are  ef¬ 
fective  is  the  factor  of  most  importance,  but  this  de¬ 
pends  upon  a  number  of  conditions  such  as  the  illumi¬ 
nation  produced  by  the  beam  at  various  distances,  the 
atmospheric  conditions,  the  position  of  the  observer, 
the  size,  pattern,  color,  and  reflection-factor  of  the  ob¬ 
ject,  and  the  color,  pattern,  and  reflection-factor  of  the 
background.  These  are  too  involved  to  be  discussed 
here,  but  it  may  be  stated  that  under  ordinary  condi¬ 
tions  these  powerful  lights  are  effective  at  distances  of 
several  miles.  According  to  recent  work,  it  appears 
that  the  range  of  a  search-light  in  revealing  a  given  ob¬ 
ject  under  fixed  conditions  varies  about  as  the  fourth 
root  of  its  intensity. 

Although  the  metallic  parabolic  reflector  is  used  in 
the  most  powerful  search-lights,  there  have  been  many 
other  developments  adapted  to  warfare.  Fresnel 
lenses  have  been  used  above  the  arc  for  search-lights 
whose  beams  are  directed  upward  in  search  of  aircraft, 
thus  replacing  the  mirror  below  the  arc,  which,  owing 
to  its  position,  is  always  in  danger  of  deterioration  by 
the  hot  carbon  particles  dropping  upon  it.  For  short 


ARTIFICIAL  LIGHT  IN  WARFARE  191 

ranges  incandescent  filament  lamps  have  been  used  with 
success.  Oxyacetylene  equipment  has  found  applica¬ 
tion,  owing  to  its  portability.  The  oxyacetylene  flame 
is  concentrated  upon  a  small  pellet  of  ceria,  which  pro¬ 
vides  a  brilliant  source  of  small  dimensions.  A  tank 
containing  about  1000  liters  of  dissolved  acetylene  and 
another  containing  about  1100  liters  of  oxygen  supply 
the  fuel.  A  beam  having  an  intensity  of  about  1,500,- 
000  candles  is  obtained  with  a  consumption  of  40  liters 
of  each  of  the  gases  per  hour.  At  this  rate  the  search¬ 
light  may  be  operated  twenty  hours  without  replen¬ 
ishing. 

Although  the  beacon-light  for  nocturnal  airmen  is  a 
development  which  will  assume  much  importance  in 
peaceful  activities,  it  was  developed  chiefly  to  meet  the 
requirements  of  warfare.  These  do  not  differ  ma¬ 
terially  from  those  which  guide  the  mariner,  except 
that  the  traveler  in  the  aerial  ocean  is  far  above  the 
plane  on  which  the  beacon  rests.  For  this  reason  the 
lenses  are  designed  to  send  light  generally  upward.  In 
foreign  countries  several  types  of  beacons  for  aerial 
navigation  have  been  in  use.  In  one  the  light  from  the 
source  is  freely  emitted  in  all  upward  directions,  but 
the  light  normally  emitted  into  the  lower  hemisphere 
is  turned  upward  by  means  of  prisms.  In  a  more 
elaborate  type,  belts  of  lenses  are  arranged  so  as  to 
send  light  in  all  directions  above  the  horizontal  plane. 
A  flashing  apparatus  is  used  to  designate  the  locality 
by  the  number  or  character  of  the  flashes.  Electric 
filaments  and  acetylene  flames  have  been  used  as  the 
light-sources  for  this  purpose.  In  another  type  the 
light  is  concentrated  in  one  azimuth  and  the  whole 


192 


ARTIFICIAL  LIGHT 


beacon  is  revolved.  Portable  beacons  employing  gas 
were  used  during  the  war  on  some  of  the  flying-fields 
near  the  battle  front. 

All  kinds  of  lighting  and  lighting-devices  were  used, 
depending  upon  the  needs  and  material  available. 
Even  self-luminous  paint  was  used  for  various  pur¬ 
poses  at  the  front,  as  well  as  for  illuminating  watch- 
dials  and  the  scales  of  instruments.  Wooden  buttons 
two  or  three  inches  in  diameter  covered  with  self- 
luminous  paint  could  be  fixed  wherever  desired  and 
thus  serve  as  landmarks.  They  are  visible  only  at 
short  distances  and  the  feebleness  of  their  light  made 
them  particularly  valuable  for  various  purposes  at  the 
battle  front.  They  could  be  used  in  the  hand  for  giv¬ 
ing  optical  signals  at  a  short  distance  where  silence  was 
essential.  Self-luminous  arrows  and  signs  directed 
troops  and  trucks  at  night  and  even  stretcher-bearers 
have  borne  self-luminous  marks  on  their  backs  in  order 
to  identify  them  to  their  friends. 

Somewhat  analogous  to  this  application  of  luminous 
paint  is  the  use  of  blue  light  at  night  on  battle-ships 
and  other  vessels  in  action  or  near  the  enemy.  Several 
years  ago  a  Brazilian  battle-ship  built  in  this  country 
was  equipped  with  a  dual  lighting-system.  The  extra 
one  used  deep-blue  light,  which  is  very  effective  for 
eyes  adapted  to  darkness  or  to  very  low  intensities  of 
illumination  and  is  a  short-range  light.  Owing  to  the 
low  luminous  intensity  of  the  blue  lights  they  do  not 
carry  far ;  and  furthermore,  it  is  well  established  that 
blue  light  does  not  penetrate  as  far  through  ordinary 
atmosphere  as  lights  of  other  colors  of  the  same  in¬ 
tensity. 


ARTIFICIAL  LIGHT  IN  WARFARE  193 


The  war  has  been  responsible  for  great  strides  in 
certain  directions  in  the  development  and  nse  of  arti¬ 
ficial  light  and  the  era  of  peace  will  inherit  these  de¬ 
velopments  and  will  adapt  them  to  more  constructive 
purposes. 


XV 

SIGNALING 


From  earliest  times  the  beacon-lire  has  sent  forth 
messages  from  hilltops  or  across  inaccessible  places. 
In  this  country,  when  the  Indian  was  monarch  of  the 
vast  areas  of  forest  and  prairie,  he  spread  news  broad¬ 
cast  to  roving  tribesmen  by  means  of  the  signal-lire, 
and  he  flashed  his  code  by  covering  and  uncovering  it. 
Castaways,  whether  in  fiction  or  in  reality,  instinctively 
turn  to  the  beacon-fire  as  a  mode  of  attracting  a  passing 
ship.  On  every  hand  throughout  the  ages  this  simple 
means  of  communication  has  been  employed;  there¬ 
fore,  it  is  not  surprising  that  mankind  has  applied  his 
ingenuity  to  the  perfection  of  signaling  by  means  of 
light,  which  has  its  own  peculiar  fields  and  advantages. 
Of  course,  wireless  telephony  and  telegraphy  will  re¬ 
place  light-signaling  to  some  extent,  but  there  are  many 
fields  in  which  the  last-named  is  still  supreme.  In 
fact,  during  the  recent  war  much  use  was  made  of  light 
in  this  manner  and  devices  were  developed  despite  the 
many  other  available  means  of  signaling.  One  of  the 
chief  advantages  of  light  as  a  signal  is  that  it  is  so 
easily  controlled  and  directed  in  a  straight  line.  Wire¬ 
less  waves,  for  example,  are  radiated  broadcast  to  be 
intercepted  by  the  enemy. 

The  beginning  of  light-signaling  is  hidden  in  the  ob¬ 
scurity  of  the  past.  Of  course,  the  most  primitive 

104 


SIGNALING 


195 


light-signals  were  wood  fires,  but  it  is  likely  that  man 
early  utilized  the  mirror  to  reflect  the  sun’s  image  and 
thus  laid  the  foundation  of  the  modem  heliograph. 
The  Book  of  Job,  which  is  probably  one  of  the  oldest 
writings  available,  mentions  molten  mirrors.  The 
Egyptians  in  the  time  of  Moses  used  mirrors  of 
polished  brass.  Euclid  in  the  third  century  before  the 
Christian  era  is  said  to  have  written  a  treatise  in  which 
he  discussed  the  reflection  of  light  by  concave  mirrors. 
John  Pechham,  Archbishop  of  Canterbury  in  the  thir¬ 
teenth  century,  described  mirrors  of  polished  steel  and 
of  glass  backed  with  lead.  Mirrors  of  glass  coated 
with  an  allow  of  tin  and  mercury  were  made  by  the 
Venetians  in  the  sixteenth  century.  Huygens  in  the 
seventeenth  century  studied  the  laws  of  refraction  and 
reflection  and  devised  optical  apparatus  for  various 
purposes.  However,  it  was  not  until  the  eighteenth 
century  that  any  noteworthy  attempts  were  made  to 
control  artificial  light  for  practical  purposes.  Dol- 
lond  in  1757  was  the  first  to  make  achromatic  lenses  by 
using  combinations  of  different  glasses.  Lavoisier  in 
1774  made  a  lens  about  four  feet  in  diameter  by  con¬ 
structing  a  cell  of  two  concave  glasses  and  filling  it 
with  water  and  other  liquids.  It  is  said  that  he  ignited 
wood  and  melted  metals  by  concentrating  the  sun’s 
image  upon  them  by  means  of  this  lens.  About  that 
time  Buffon  made  a  built-up  parabolic  mirror  by  means 
of  several  hundred  small  plane  mirrors  set  at  the 
proper  angles.  With  this  he  set  fire  to  wood  at  a  dis¬ 
tance  of  more  than  two  hundred  feet  by  concentrating 
the  sun’s  rays.  He  is  said  also  to  have  made  a  lens 
from  a  solid  piece  of  glass  by  grinding  it  in  concentric 


196 


ARTIFICIAL  LIGHT 


steps  similar  to  the  designs  worked  out  by  Fresnel 
seventy  years  later.  These  are  examples  of  the  early 
work  which  laid  the  foundation  for  the  highly  perfected 
control  of  light  of  the  present  time. 

While  engaged  in  the  survey  of  Ireland,  Thomas 
Drummond  in  1826  devised  apparatus  for  signaling 
many  miles,  thus  facilitating  triangulation.  Distances 
as  great  as  eighty  miles  were  encountered  and  it  ap¬ 
peared  desirable  to  have  some  method  for  seeing  a 
point  at  these  great  distances.  Gauss  in  1822  used  the 
reflection  of  the  sun’s  image  from  a  plane  mirror  and 
Drummond  also  tried  this  means.  The  latter  was  suc¬ 
cessful  in  signaling  45  miles  to  a  station  which  because 
of  haze  could  not  be  seen,  or  even  the  hill  upon  which 
it  rested.  Having  demonstrated  the  feasibility  of  the 
plan,  he  set  about  making  a  device  which  would  in¬ 
clude  a  powerful  artificial  light  in  order  to  be  inde¬ 
pendent  of  the  sun.  In  earlier  geodetic  surveys  Ar- 
gand  lamps  had  been  employed  with  parabolic  reflectors 
and  with  convex  lenses,  but  apparently  these  did  not 
have  a  sufficient  range.  Fresnel  and  Arago  con¬ 
structed  a  lens  consisting  of  a  series  of  concentric  rings 
which  were  cemented  together,  and  on  placing  this  be¬ 
fore  an  Argand  lamp  possessing  four  concentric  wicks, 
they  obtained  a  light  which  was  observed  at  forty-eight 
miles. 

Despite  these  successes,  Drummond  believed  the 
parabolic  mirror  and  a  more  powerful  light-source  af¬ 
forded  the  best  combination  for  a  signal-light.  In 
searching  for  a  brilliant  light-source  he  experimented 
with  phosphorus  burning  in  oxygen  and  with  various 
billiant  pyrotechnical  preparations.  However,  flames 


SIGNALING 


197 


were  unsteady  and  generally  unsuitable.  He  then 
turned  in  the  direction  which  led  to  his  development  of 
the  lime-light.  In  his  first  apparatus  he  used  a  small 
sphere  of  lime  in  an  alcohol  flame  and  directed  a  jet  of 
oxygen  through  the  flame  upon  the  lime.  He  thereby 
obtained,  according  to  his  own  description  in  1826, 

a  light  so  intense  that  when  placed  in  the  focus  of  a 
reflector  the  eye  could  with  difficulty  support  its  splen¬ 
dor,  even  at  a  distance  of  forty  feet,  the  contour  being 
lost  in  the  brilliancy  of  the  radiation. 

He  then  continued  to  experiment  with  various  oxides, 
including  zirconia,  magnesia,  and  lime  from  chalk  and 
marble.  This  was  the  advent  of  the  lime-light,  which 
should  bear  Drummond’s  name  because  it  was  one  of 
the  greatest  steps  in  the  evolution  of  artificial  light. 

By  means  of  this  apparatus  in  the  survey,  signals 
were  rendered  visible  at  distances  as  great  as  one  hun¬ 
dred  miles.  Drummond  proposed  the  use  of  this  light- 
source  in  the  important  lighthouses  at  that  time  and 
foresaw  many  other  applications.  The  lime-light 
eventually  was  extensively  used  as  a  light-signaling 
device.  The  heliograph,  which  utilizes  the  sun  as  a 
light-source,  has  been  widely  used  as  a  light-signaling 
apparatus  and  Drummond  perhaps  was  the  first  to 
utilize  artificial  light  with  it.  The  disadvantage  of  the 
heliograph  is  the  undependability  of  the  sun.  With 
the  adoption  of  artificial  light,  various  optical  devices 
have  come  into  use. 

Philip  Colomb  perhaps  is  deserving  of  the  credit  of 
initiating  modern  signaling  by  flashing  a  code.  He  be¬ 
gan  work  on  such  a  system  in  1858  and  as  an  officer  in 


198 


ARTIFICIAL  LIGHT 


the  British  Navy  worked  hard  to  introduce  it.  Finally, 
in  1867,  the  British  Navy  adopted  the  flashing-system, 
in  which  a  light-source  is  exposed  and  eclipsed  in  such 
a  manner  as  to  represent  dots  and  dashes  analogous 
to  the  Morse  code.  At  first  the  rate  of  transmission 
of  words  was  from  seven  to  ten  per  minute.  Recently 
much  more  sensitive  apparatus  is  available,  and  with 
such  devices  the  rate  is  limited  only  by  the  sluggishness 
of  the  visual  process.  This  initial  system  was  very 
successful  in  the  British  Navy  and  it  was  soon  found 
that  a  fleet  could  be  handled  with  ease  and  safety  in 
darkness  or  in  fog.  Inasmuch  as  the  “ dot-and-dash’ ’ 
system  requires  only  two  elements,  it  may  be  trans¬ 
mitted  by  various  means.  A  lantern  may  be  swung  in 
short  and  long  arcs  or  dipped  accordingly. 

The  blinker  or  pulsating  light-signal  consists  of  a 
single  light-source  mechanically  occulted.  It  is  con¬ 
trolled  by  means  of  a  telegraph-key  and  the  code  may 
be  rapidly  transmitted.  The  search-light  affords  a 
means  for  signaling  great  distances,  even  in  the  day¬ 
time.  The  light  is  usually  mechanically  occulted  by  a 
quick-acting  shutter,  but  recently  another  system  has 
been  devised.  In  the  latter  the  light  itself  is  controlled 
by  means  of  an  electrical  shunt  across  the  arc.  In 
this  manner  the  light  is  dimmed  by  shunting  most  of 
the  current,  thereby  producing  the  same  effect  as  actu¬ 
ally  eclipsing  the  light  with  a  mechanical  shutter.  By 
means  of  the  search-light  signals  are  usually  visible 
as  far  as  the  limitations  of  the  earth’s  curvature  will 
permit.  By  directing  the  beam  against  a  cloud,  signals 
have  been  observed  at  a  distance  of  one  hundred  miles 
from  the  search -light  despite  intervening  elevated  land 


SIGNALING 


199 


or  the  curvature  of  the  ocean ’s  surface.  By  means  of 
small  search-lights  it  is  easy  to  send  signals  ten  miles. 

This  kind  of  apparatus  has  the  advantage  of  being 
selective ;  that  is,  the  signals  are  not  visible  to  persons 
a  few  degrees  from  the  direction  of  the  beam.  One  of 
the  most  recent  developments  has  been  a  special  tung¬ 
sten  filament  in  a  gas-filled  bulb  placed  at  the  focus  of 
a  small  parabolic  mirror.  The  beam  is  directed  by 
means  of  sights  and  the  flashes  are  obtained  by  inter¬ 
rupting  the  current  by  means  of  a  trigger-switch.  The 
filament  is  so  sensitive  that  signals  may  be  sent  faster 
than  the  physiological  process  of  vision  will  record. 
With  the  advent  of  wireless  telegraphy  light-signaling 
for  long  distances  was  temporarily  eclipsed,  but  during 
the  recent  war  it  was  revived  and  much  development 
work  was  prosecuted. 

The  Ardois  system  consists  of  four  lamps  mounted 
in  a  vertical ‘line  as  high  as  possible.  Each  lamp  is 
double,  containing  a  red  and  a  white  light,  and  these 
lights  are  controlled  from  a  keyboard.  A  red  light 
indicates  a  dot  in  the  Morse  code  and  a  white  light  indi¬ 
cates  a  dash.  The  keys  are  numbered  and  lettered, 
so  that  the  system  may  be  operated  by  any  one.  Vari¬ 
ous  other  systems  employing  colored  lights  have  been 
used,  but  they  are  necessarily  short-range  signals. 
Another  example  is  the  semaphore.  When  used  at 
night,  tungsten  lamps  in  reflectors  indicate  the  posi¬ 
tions  of  the  arms.  The  advantage  of  these  signals  over 
the  flashing-system  is  that  each  signal  is  complete  and 
easy  to  follow.  The  flashing-system  is  progressive  and 
must  be  carefully  followed  in  order  to  obtain  the  mean¬ 
ing  of  the  dots  and  dashes. 


200 


ARTIFICIAL  LIGHT 


Smaller  signal-lamps  using  acetylene  have  been  em¬ 
ployed  in  the  forestry  service  and  in  other  activities 
where  a  portable  device  is  necessary.  In  one  type,  a 
mixture-tank  containing  calcium  carbide  and  water  is 
of  sufficient  capacity  for  three  hours  of  signaling.  A 
small  pilot-light  is  permitted  to  burn  constantly  and 
the  flashes  are  obtained  by  operating  a  key  which  in¬ 
creases  the  gas-pressure.  The  light  flares  as  long  as 
the  key  in  depressed.  The  range  of  this  apparatus  is 
from  ten  to  twenty  miles.  An  electric  lamp  supplied 
from  a  storage  battery  has  been  designed  for  geodetic 
operations  in  mountainous  districts  where  it  is  desired 
to  send  signals  as  far  as  one  hundred  miles.  Tests 
show  that  this  device  is  a  hundred  and  fifty  times  more 
powerful  than  the  ordinary  acetylene  signal-lamp,  and 
it  is  thought  that  with  this  new  electric  lamp  haze  and 
smoke  will  seldom  prevent  observations. 

Certain  fixed  lights  are  required  by  law  on  a  vessel 
at  night.  When  it  is  under  way  there  must  be  a  white 
light  at  the  masthead,  a  starboard  green  light,  a  port 
red  light,  a  white  range-light,  and  a  white  light  at  the 
stern.  The  masthead  light  is  designed  to  emit  light 
through  a  horizontal  arc  of  twenty  points  of  the  com¬ 
pass,  ten  on  each  side  of  dead  ahead.  This  light  must 
be  visible  at  a  distance  of  five  miles.  The  port  and 
starboard  lights  operate  through  a  horizontal  arc  of 
twenty  points  of  the  compass,  the  middle  of  which  is 
dead  ahead.  They  are  screened  so  as  not  to  be  visible 
across  the  bow  and  they  must  be  intense  enough  to  be 
visible  two  miles  ahead.  The  masthead  light  is  carried 
on  the  foremast  and  the  range-light  on  the  mainmast, 
at  an  elevation  fifteen  feet  higher  than  the  former. 


SIGNALING 


201 


The  range-light  emits  light  toward  all  points  of  the 
compass  and  must  be  intense  enough  to  be  seen  at  a 
distance  of  three  miles.  The  stern  light  is  similar  to 
the  masthead,  but  its  light  must  not  be  visible  forward 
of  the  beam.  When  a  vessel  is  towing  another  it  must 
display  two  or  three  lights  in  a  vertical  line  with  the 
masthead  light  and  similar  to  it.  The  lights  are  spaced 
about  six  feet  apart,  and  two  extra  ones  indicate  a 
short  tow  and  three  a  long  one.  A  vessel  over  a  hun¬ 
dred  and  fifty  feet  long  when  at  anchor  is  required  to 
display  a  white  light  forward  and  aft,  each  visible 
around  the  entire  horizon.  These  and  many  other 
specifications  indicate  how  artificial  light  informs  the 
mariner  and  makes  for  order  in  shipping.  Without 
artificial  light  the  waterways  would  be  trackless  and 
chaos  would  reign. 

The  distress  signals  of  a  vessel  are  rockets,  but  any 
burning  flame  also  serves  if  rockets  are  unavailable. 
Fireworks  were  known  many  centuries  ago  and  doubt¬ 
less  the  possibilities  of  signaling  by  means  of  rockets 
have  long  been  recognized.  An  early  instance  of  scien¬ 
tific  interest  in  rockets  and  their  usefulness  is  that  of 
Benjamin  Robins  in  1749.  While  he  was  witnessing 
a  display  of  fireworks  in  London  it  occurred  to  him  that 
it  would  be  of  interest  to  measure  the  height  to  which 
the  rockets  ascended  and  to  determine  the  ranges  at 
which  they  were  visible.  His  measurements  indicated 
that  the  rockets  ascended  usually  to  a  height  of  440 
yards,  but  some  of  them  attained  altitudes  as  high  as 
615  yards.  He  then  had  some  special  ones  made  and 
despatched  letters  to  friends  in  three  different  locali¬ 
ties,  at  distances  as  great  as  50  miles,  asking  them  to 


ARTIFICIAL  LIGHT 


202 

observe  at  a  certain  time,  when  the  rockets  were  to  be 
sent  up  in  the  outskirts  of  London.  Some  of  these 
rockets  rose  to  altitudes  as  great  as  600  yards  and  were 
distinctly  seen  by  observers  38  miles  away.  Later  he 
made  rockets  which  ascended  as  high  as  1200  yards  and 
concluded  that  this  was  a  practical  means  of  signaling. 
Since  that  time  and  especially  during  the  recent  war, 
rockets  have  served  well  in  signaling  messages. 

The  self-propelled  rockets  have  not  been  altered  in 
essential  features  since  the  remote  centuries  when  the 
Chinese  first  used  them  in  celebrations.  A  cylindrical 
shell  is  mounted  on  a  wooden  stick  and  when  the  pow¬ 
der  in  the  shell  burns  the  hot  gases  are  ejected  so  vio¬ 
lently  downward  that  the  reaction  drives  the  shell  up¬ 
ward.  At  a  certain  point  in  the  air,  various  signals 
burst  forth,  which  vary  in  character  and  color.  One 
of  the  advantages  of  the  rocket  is  that  it  contains 
within  itself  the  force  of  propulsion ;  that  is,  no  gun  is 
necessary  to  project  it.  The  illuminating  compounds 
and  various  details  are  similar  to  those  of  the  illumin¬ 
ating  shells  described  in  another  chapter. 

At  present  the  rocket  is  not  scientifically  designed 
to  obtain  the  greatest  efficiency  of  propulsion,  but  its 
simplicity  in  this  respect  is  one  of  its  chief  advantages. 
If  the  self-propelled  rocket  becomes  the  projectile  of 
the  future,  as  some  have  ventured  to  predict,  much  con¬ 
sideration  must  be  given  to  the  design  of  the  orifice 
through  which  the  gases  violently  escape  in  order  that 
the  best  efficiency  of  propulsion  may  be  attained. 
There  are  other  details  in  which  improvements  may  be 
made.  The  combustion  products  of  the  black  powder 
which  are  not  gaseous  equal  about  one  third  the  weight 


SIGNALING 


203 


of  the  powder.  This  represents  inefficient  propulsion. 
Furthermore,  during  recent  years  much  information 
has  been  gained  pertaining  to  the  air-resistance  which 
can  be  applied  to  advantage  in  designing  the  form  of 
rockets. 

Besides  the  various  rockets,  signal-lights  have  been 
constructed  to  be  tired  from  guns  and  pistols.  Dur¬ 
ing  the  recent  war  the  airman  in  the  dark  heights  used 
the  pistol  signal-light  effectively  for  communication. 
These  devices  emitted  stars  either  singly  or  in  succes¬ 
sion,  and  the  color  of  these  stars  as  well  as  their  num¬ 
ber  and  sequence  gave  significance  to  the  signal. 
Some  of  these  light-signals  were  provided  with  para¬ 
chutes  and  were  long-burning ;  that  is,  light  was 
emitted  for  a  minute  or  two.  There  are  many  varia¬ 
tions  possible  and  a  great  many  different  kinds  of 
light-signals  of  this  character  were  used.  In  the 
front-line  trenches  and  in  advances  they  were  used 
when  telephone  service  was  unavailable.  The  airman 
directed  artillery  fire  by  means  of  his  pistol-light. 
Rockets  brought  aid  to  the  foundered  ship  or  to  the 
life-boats.  The  signal-tube  which  burned  red,  green, 
or  white  was  held  in  the  hand  or  laid  on  the  ground 
and  it  often  told  its  story.  For  many  years  such  a 
device  dropped  from  the  rear  of  the  railroad  train  has 
kept  the  following  train  at  a  safe  distance.  A  device 
was  tried  out  in  the  trenches,  during  the  war,  which 
emitted  a  flame.  This  could  be  varied  in  color  to 
serve  as  a  signal  and  the  apparatus  had  sufficient  ca¬ 
pacity  for  thirty  hours  ’  burning.  This  could  also  be 
used  as  a  weapon,  or  when  reduced  in  intensity  it 
served  as  a  flash-light. 


204 


ARTIFICIAL  LIGHT 


For  many  years  experiments  have  been  made  upon 
the  use  of  the  invisible  rays  which  accompany  visible 
rays.  The  practicability  of  signaling  with  invisible 
rays  depends  upon  producing  them  efficiently  in  suffi¬ 
cient  quantity  and  upon  separating  them  from  the  vis¬ 
ible  rays  which  accompany  them.  Some  successful  re¬ 
sults  were  obtained  with  a  6-volt  electric  lamp  possess¬ 
ing  a  coiled  filament  at  the  focus  of  a  lens  three  inches 
in  diameter  and  twelve  inches  in  focal  length.  This 
gave  a  very  narrow  beam  visible  only  in  the  neighbor¬ 
hood  of  the  observation  post  to  which  the  signals  were 
directed.  The  beam  was  directed  by  telescopic  sights. 
During  the  day  a  deep  red  filter  was  placed  over  the 
lamp  and  the  light  was  invisible  to  an  observer  unless 
he  was  equipped  with  a  similar  red  screen  to  eliminate 
the  daylight.  It  is  said  that  signals  were  distinguished 
at  a  distance  of  six  miles.  By  night  a  screen  was  used 
which  transmitted  only  the  ultraviolet  rays-  and  the 
observer’s  telescope  was  provided  with  a  fluorescent 
screen  in  its  focal  plane.  The  ultraviolet  rays  fall¬ 
ing  upon  this  screen  were  transformed  into  visible  rays 
by  the  phenomenon  of  fluorescence.  The  range  of  this 
device  was  about  six  miles.  For  naval  convoys  lamps 
are  required  to  radiate  toward  all  points  of  the  com¬ 
pass.  For  this  purpose  a  quartz  mercury-arc  which 
is  rich  in  ultraviolet  rays  was  surrounded  with  a  chim¬ 
ney  which  transmitted  the  ultraviolet  rays  efficiently 
and  absorbed  all  visible  rays  excepting  violet  light. 
The  lamp  appeared  a  deep  violet  color  at  close  range, 
but  the  faintly  visible  light  which  it  transmitted  was  not 
seen  at  a  distance.  A  distant  observer  picks  up  the 
invisible  ultraviolet  ‘ 4 light”  by  means  of  a  special 


SIGNALING 


205 


optical  device  having  a  fluorescent  screen  of  barium- 
platino-cyanide.  This  device  had  a  range  of  about 
four  miles. 

Light-signals  are  essential  for  the  operation  of  rail¬ 
ways  at  night  and  they  have  been  in  use  for  many 
years.  In  this  field  the  significance  of  light-signals  is 
based  almost  universally  on  color.  The  setting  of  a 
switch  is  indicated  by  the  color  of  the  light  that  it 
shows.  With  the  introduction  of  the  semaphore  sys¬ 
tem,  in  which  during  the  day  the  position  of  the  arm 
is  significant,  colored  glasses  were  placed  on  the  op¬ 
posite  end  of  the  arm  in  such  a  manner  that  a  certain 
colored  glass  would  appear  before  the  light-source  for 
•  a  certain  position  of  the  arm.  A  kerosene  flame  behind 
a  glass  lens  was  the  lamp  used,  and,  for  example,  red 
meant  4 4 Stop,’ ’  green  counseled  “Caution,”  and  clear 
or  white  indicated  “All  clear. ”  For  many  years  the 
kerosene  lamp  has  been  used,  but  recently  the  electric 
filament  lamp  is  being  installed  to  some  extent  for  this 
purpose.  In  fact,  on  one  railroad  at  least,  tungsten 
lamps  are  used  for  light-signals  by  day  as  well  as  by 
night.  Three  signals — red,  green,  and  white — are 
placed  in  a  vertical  line  and  behind  each  lens  are  two 
lamps,  one  operating  at  high  efficiency  and  one  at  low 
efficiency  to  insure  against  the  failure  of  the  signal. 
The  normal  daylight  range  is  about  three  thousand  feet 
and  under  the  worst  conditions  when  opposed  to  di¬ 
rect  sunlight,  the  range  is  not  less  than  two  thousand 
feet.  It  is  said  that  these  lights  are  seen  more  easily 
than  semaphore  arms  under  all  circumstances  and  that 
they  show  two  or  three  times  as  far  as  the  latter  during 
a  snow-storm. 


206 


ARTIFICIAL  LIGHT 


Tlie  standard  colors  for  light-signals  as  adopted  by 
the  Railway  Signal  Association  are  red,  yellow,  green, 
blue,  purple,  and  lunar  white.  These  are  specified  as 
to  the  amount  of  the  various  spectral  colors  which  they 
transmit  when  the  light-source  is  the  kerosene  flame. 
Obviously,  the  colors  generally  appear  different  when 
another  illuminant  is  used.  The  blue  and  purple  are 
short-range  signals,  but  the  effective  range  of  the  best 
railway  signal  employing  a  kerosene  flame  is  only  about 
four  miles. 

It  has  been  shown  that  the  visibility  of  point  sources 
of  white  light  in  clear  atmosphere,  for  distances  up  to 
a  mile  at  least,  is  proportional  to  their  candle-power 
and  inversely  proportional  to  the  square  of  the  dis¬ 
tance.  Apparently  the  luminous  intensities  of  signal- 
lamps  required  in  clear  weather  in  order  that  they  may 
be  visible  must  be  0.43  candles  for  one  nautical  mile, 
1.75  candles  for  two  nautical  miles,  and  11  candles  for 
five  nautical  miles.  From  the  data  available  it  appears 
that  a  red  or  a  white  signal-light  will  be  easily  visible 
at  a  distance  in  nautical  miles  equal  to  the  square  root 
of  its  candle-power  in  that  direction.  The  range  in 
nautical  miles  of  a  green  light  apparently  is  propor¬ 
tional  to  the  cube  root  of  the  candle-power.  Whether 
or  not  these  relations  between  the  range  in  miles  and 
the  luminous  intensity  in  candles  hold  for  greater  dis¬ 
tances  than  those  ordinarily  encountered  has  not  been 
determined,  but  it  is  interesting  to  note  that  the  square 
root  of  the  luminous  intensity  of  the  Navesink  Light 
at  the  entrance  to  New  York  Harbor  is  about  7000. 
Could  this  light  be  seen  at  a  distance  of  seven  thousand 
miles  through  ordinary  atmosphere! 


SIGNALING 


207 


The  most  distinctive  colored  lights  are  red,  yellow, 
green,  and  bine.  To  these  white  (clear)  and  purple 
have  been  add*ed  for  signaling-purposes.  Yellow  is 
intense,  but  it  may  be  confused  with  “white”  or  clear. 
Blue  and  purple  as  obtained  from  the  pre’sent  prac¬ 
ticable  light-sou-rces  are  of  low  intensity.  This  leaves 
red,  green,  and  clear  as  the  most  generally  satisfactory 
signal-lights. 

There  are  numerous  other  applications,  especially 
indoors.  Some  of  these  have  been  devised  for  special 
needs,  but  there  are  many  others  which  are  general, 
such  as  for  elevators,  telephones,  various  call  sys¬ 
tems,  and  traffic  signals.  Light  has  the  advantages  of 
being  silent  and  controllable  as  to  position  and  direc¬ 
tion,  and  of  being  a  visible  signal  at  night.  Thus,  in 
another  field  artificial  light  has  responded  to  the  de¬ 
mands  of  civilization. 


XVI 

THE  COST  OF  LIGHT 


Artificial  light  is  so  superior  to  natural  light  in 
many  respects  that  mankind  has  acquired  the  habit  of 
retiring  many  hours  after  darkness  has  fallen,  a  result 
of  which  has  brought  forth  the  issue  known  as  “day¬ 
light  saving.”  Doubtless,  daylight  should  be  used 
whenever  possible,  but  there  are  two  sides  to  the  ques¬ 
tion.  In  the  first  place,  it  costs  something  to  bring 
daylight  indoors.  The  architectural  construction  of 
windows  and  skylights  increases  the  cost  of  daylight. 
Light-courts,  by  sacrificing  valuable  floor-area,  add  to 
the  expense.  The  maintenance  of  windows  and  sky 
lights  is  an  appreciable  item.  Considering  these  and 
other  factors,  it  can  be  seen  that  daylight  indoors  is  ex¬ 
pensive  ;  and  as  it  is  also  undependable,  a  supplement¬ 
ary  system  of  artificial  lighting  is  generally  necessary. 
In  fact,  it  is  easy  to  show  in  some  cases  that  artificial 
lighting  is  cheaper  than  natural  lighting. 

The  average  middle-class  home  is  now  lighted  arti¬ 
ficially  for  about  $15.00  to  $25.00  per  year,  with  con¬ 
venient  light-sources  which  are  available  at  all  times. 
There  is  no  item  in  the  household  budget  which  re¬ 
turns  as  much  satisfaction,  comfort,  and  happiness  in 
proportion  to  its  cost  as  artificial  light.  It  is  an  ar¬ 
tistic  medium  of  great  potentiality,  and  light  in  a  nar¬ 
row  utilitarian  sense  is  always  a  by-product  of  ar- 

208 


THE  COST  OF  LIGHT 


209 


tistic  lighting.  The  insignificant  cost  of  modern  light¬ 
ing  may  be  emphasized  in  many  ways.  The  interest  on 
the  investment  in  a  picture  or  a  vase  which  cost  $25.00 
will  usually  cover  the  cost  of  operating  any  decora¬ 
tive  lamp  in  the  home.  A  great  proportion  of  the  in¬ 
vestment  in  personal  property  in  a  home  is  charge¬ 
able  to  an  attempt  to  beautify  the  surroundings.  The 
interest  on  only  a  small  portion  of  this  investment 
will  pay  for  artistic  and  utilitarian  artificial  lighting 
in  the  home.  The  cost  of  washing  the  windows  of  the 
average  house  may  be  as  great  as  the  cost  of  artificial 
lighting  and  is  usually  at  least  a  large  fraction  of  the 
latter.  It  would  become  monotonous  to  cite  the  va¬ 
rious  examples  of  the  insignificant  cost  of  artificial 
light  and  its  high  return  to  the  user.  The  example  of 
the  home  has  been  chosen  because  the  reader  may  eas¬ 
ily  carry  the  analysis  further.  The  industries  where 
costs  are  analyzed  are  now  looking  upon  adequate  and 
proper  lighting  as  an  asset  which  brings  in  profits 
by  increasing  production,  by  decreasing  spoilage,  and 
by  decreasing  the  liability  of  accidents. 

Inasmuch  as  daylight  saving  became  an  issue  during 
the  recent  war  and  is  likely  to  remain  a  matter  of 
concern,  its  history  is  interesting.  One  of  the  out¬ 
standing  differences  between  primitive  and  civilized 
beings  is  their  hours  of  activities.  The  former  auto¬ 
matically  adjusted  themselves  to  daylight,  but  as  civ¬ 
ilization  advanced,  the  span  of  activities  began  to  ex¬ 
tend  more  and  more  beyond  the  coming  of  darkness. 
Finally,  in  many  activities  the  work-day  was  extended 
to  twenty-four  hours.  There  can  be  no  insurmount¬ 
able  objection  to  working  at  night  with  a  proper  ar- 


210 


ARTIFICIAL  LIGHT 


rangement  of  the  periods  of  work;  in  fact,  the  cost  of 
living  would  be  greatly  increased  if  the  overhead 
charges  represented  by  such  items  as  machinery  and 
buildings  were  allowed  to  be  carried  by  the  decreased 
products  of  a  shortened  period  of  production.  There 
cannot  be  any  basic  objection  to  artificial  lighting,  be¬ 
cause  most  factories,  for  example,  may  be  better  illum¬ 
inated  by  artificial  than  by  natural  light. 

Of  course,  the  lag  of  comfortable  temperature  be¬ 
hind  daylight  is  responsible  to  some  extent  for  a  nat¬ 
ural  shifting  of  the  ordinary  working-day  somewhat 
behind  the  sun.  The  chill  of  dawn  tends  to  keep  man¬ 
kind  in  bed  and  the  cheer  of  artificial  light  and  the  pe¬ 
riod  of  recreation  in  the  evening  tends  to  keep  the 
civilized  races  out  of  bed.  There  are  powerful  influ¬ 
ences  always  at  work  and  despite  the  desirable  features 
of  daylight-saving,  mankind  will  always  tend  to  lag. 
As  years  go  by,  doubtless  it  will  be  necessary  to  make 
the  shift  again  and  again.  It  seems  certain  that 
throughout  the  centuries  thoughtful  persons  have  seen 
the  difficulty  of  rousing  man  from  his  warm  bed  in  the 
early  morning  and  have  recognized  a  simple  solution 
in  turning  the  hands  of  the  clock  ahead.  Among  the 
earliest  advocates  of  daylight  saving  during  modern 
times,  when  it  became  important  enough  to  be  consid¬ 
ered  as  an  economic  issue,  was  Benjamin  Franklin. 
In  1784  he  wrote  a  masterful  -serio-comic  essay  en¬ 
titled  “An  Economical  Project ”  which  was  published 
in  the  Journal  of  Paris.  The  article,  which  appeared 
in  the  form  of  a  letter,  began  thus: 


Messieurs:  You  often  entertain  us  with  accounts 


THE  COST  OF  LIGHT 


211 


of  new  discoveries.  Permit  me  to  communicate  to  the 
public  through  your  paper  one  that  has  lately  been 
made  by  myself  and  which  I  conceive  may  be  of  great 
utility. 

I  was  the  other  evening  in  a  grand  company  where 
the  new  lamp  of  Messrs.  Quinquet  and  Lange  was  in¬ 
troduced  and  much  admired  for  its  splendor;  but  a 
general  inquiry  was  made  whether  the  oil  it  consumed 
was  not  in  exact  proportion  to  the  light  it  afforded,  in 
which  case  there  would  be  no  saving  in  the  use  of  it. 
No  one  present  could  satisfy  us  on  that  point,  which 
all  agreed  ought  to  be  known,  it  being  a  very  desirable 
thing  to  lessen,  if  possible,  the  expense  of  lighting  our 
apartments,  when  every  other  article  of  family  expense 
was  so  much  augmented.  I  was  pleased  to  see  this 
general  concern  for  economy,  for  I  love  economy  ex¬ 
ceedingly. 

I  went  home,  and  to  bed,  three  or  four  hours  after 
midnight,  with  my  head  full  of  the  subject.  An  acci¬ 
dental  sudden  noise  waked  me  about  6  in  the  morning, 
when  I  was  surprised  to  find  my  room  filled  with  light, 
and  I  imagined  at  first  that  a  number  of  those  lamps 
had  been  brought  into  it ;  but,  rubbing  my  eyes,  I  per¬ 
ceived  the  light  came  in  at  the  windows.  I  got  up 
and  looked  out  to  see  what  might  be  the  occasion  of 
it,  when  I  saw  the  sun  just  rising  above  the  horizon, 
from  whence  he  poured  his  rays  plentifully  into  my 
chamber,  my  domestic  having  negligently  omitted  the 
preceding  evening  to  close  the  shutters. 

I  looked  at  my  watch,  which  goes  very  well,  and 
found  that  it  was  but  6  o’clock;  and,  still  thinking  it 
something  extraordinary  that  the  sun  should  rise  so 
early,  I  looked  into  the  almanac,  where  I  found  it  to 
be  the  hour  given  for  his  rising  on  that  day.  I  looked 
forward,  too,  and  found  he  was  to  rise  still  earlier 
every  day  till  toward  the  end  of  June,  and  that  at  no 
time  in  the  year  he  retarded  his  rising  so  long  as  till 
8  o’clock. 


212 


ARTIFICIAL  LIGHT 


Your  readers-  who,  with  me,  have  never  seen  any 
signs  of  sunshine  before  noon,  and  seldom  regard  the 
astronomical  part  of  the  almanac,  will  be  as  much  as¬ 
tonished  as  I  was  when  they  hear  of  his  rising  so  early, 
and  especially  when  I  assure  them  that  he  gives  light 
as  soon  as  he  rises.  I  am  convinced  of  this.  I  am 
certain  of  my  fact.  One  cannot  be  more  certain  ,of 
any  fact.  I  saw  it  with  my  own  eyes.  And,  having 
repeated  this  observation  the  three  following  mornings, 
I  found  always  precisely  the  same  result. 

He  then  continues  in  the  same  vein  to  show  that 
learned  persons  did  not  believe  him  and  to  point  out 
the  difficulties  which  the  pioneer  encounters.  He 
brought  out  the  vital  point  by  showing  that  if  he  had 
not  been  awakened  so  early  he  would  have  slept  six 
hours  longer  by  the  light  of  the  sun  and  in  exchange 
he  would  have  lived  six  hours  the  following  night  by 
candle-light.  He  then  mustered  ‘  ‘  the  little  arithmetic  ’ ’ 
he  was  master  of  and  made  some  serious  computations. 
He  assumed  as  the  basis  of  his  computations  that  a 
hundred  thousand  families  lived  in  Paris  and  each 
used  a  half-pound  of  candles  nightly.  He  showed  that 
between  March  20th  and  September  20th,  64,000,000 
pounds  of  wax  and  tallow  could  be  saved,  which  was 
equivalent  to  $18,000,000. 

After  these  serious  computations  he  amusingly  pro¬ 
posed  the  means  for  enforcing  the  daylight  saving. 
Obviously,  it  was  necessary  to  arouse  the  sluggards 
and  his  proposals  included  the  use  of  cannons  and 
bells.  Besides,  he  proposed  that  each  family  be  re¬ 
stricted  to  one  pound  of  candles  per  week,  that  coaches 
would  not  be  allowed  to  pass  after  sunset  except  those 
of  physicians,  etc.,  and  that  a  tax  be  placed  upon  every 


THE  COST  OF  LIGHT  213 

window  which  had  shutters.  His  closing  paragraph 
was  as  follows : 

For  the  great  benefit  of  this  discovery,  thus  freely 
communicated  and  bestowed  by  me  on  the  public,  I  de¬ 
mand  neither  place,  pension,  exclusive  privilege,  nor 
any  other  regard  whatever.  I  expect  only  to  have  the 
honor  of  it.  And  yet  I  know  there  are  little,  envious 
minds  who  will,  as  usual,  deny  me  this  and  say  that 
my  invention  was  known  to  the  ancients,  and  perhaps 
they  may  bring  passages  out  of  the  old  books  in  proof 
of  it.  I  will  not  dispute  with  these  people  that  the 
ancients  knew  not  the  sun  would  rise  at  certain  hours ; 
they  possibly  had,  as  we  have,  almanacs  that  predicted 
it ;  but  it  does  not  follow  thence  that  they  knew  he  gave 
light  as  soon  as  he  rose.  That  is  what  I  claim  as 
my  discovery.  If  the  ancients  knew  it,  it  might  have 
been  long  since  forgotten;  for  it  certainly  was  unknown 
to  the  moderns,  at  least  to  the  Parisians,  which  to  prove 
I  need  use  but  one  plain  simple  argument.  They  are 
as  well  instructed,  judicious  and  prudent  a  people  as 
exist  anywhere  in  the  world,  all  professing,  like  myself, 
to  be  lovers  of  economy,  and,  for  the  many  heavy  taxes 
required  from  them  by  the  necessities  of  the  State 
have  surely  an  abundant  reason  to  be  economical.  I 
say  it  is  impossible  that  so  sensible  a  people,  under 
such  circumstances,  should  have  lived  so  long  by  the 
smoky,  unwholesome  and  enormously  expensive  light 
of  candles,  if  they  had  really  known  that  they  might 
have  had  as  much  pure  light  of  the  sun  for  nothing. 

Franklin’s  amusing  letter  had  a  serious  aim,  for  in 
1784  family  expenses  were  much  augmented  and  ade¬ 
quate  lighting  by  means  of  candles  was  very  costly  in 
those  days.  However,  conditions  have  changed  enor¬ 
mously  in  the  past  hundred  and  thirty-five  years.  A 
great  proportion  of  the  population  lives  in  the  darker 


214 


ARTIFICIAL  LIGHT 


cities.  The  wheels  of  progress  must  be  kept  going 
continuously  in  order  to  curb  the  cost  of  living,  which 
is  constantly  mounting  higher  owing  to  the  addition  of 
conveniences  and  luxuries.  Furthermore,  the  cost  of 
light  has  so  diminished  that  it  is  not  only  a  minor  fac¬ 
tor  at  present  but  in  many  cases  is  actually  ’  paying 
dividends  in  commerce  and  industry.  It  is  paying 
dividends  of  another  kind  in  the  social  and  educational 
aspects  of  the-  home,  library,  church,  and  art  museum. 
Daylight  saving  has  much  to  commend  it,  but  the  cost 
of  daylight  and  the  value  of  artificial  light  are  impor¬ 
tant  considerations. 

The  cost  of  fuels  for  lighting  purposes  cannot  be 
thoroughly  compared  throughout  a  span  of  years  with¬ 
out  regard  to  the  fluctuating  purchasing  power  of 
money,  which  would  be  too  involved  for  consideration 
here.  However,  it  is  interesting  to  make  a  brief  sur¬ 
vey  throughout  the  past  century.  From  1800  until 
1845  whale-oil  sold  for  about  $.80  per  gallon,  but  after 
this  period  it  increased  in  value,  owing  apparently  to 
its  growing  scarcity,  until  it  reached  a  price  of  $1.75 
per  gallon  in  1855.  Fortunately,  petroleum  was  dis¬ 
covered  about  this  time,  so  that  the  oil-lamp  did  not 
become  a  luxury.  From  1800  to  1850  tallow-candles 
sold  at  approximately  20  cents  a  pound.  There  being 
six  candles  to  the  pound,  and  inasmuch  as  each  candle 
burned  about  seven  hours,  the  light  from  a  candle  cost 
about  y2  cent  per  hour.  From  1850  to  1875  tallow- 
candles  sold  at  an  average  price  of  approximately  25 
cents  a  pound.  It  may  be  interesting  to  know  that 
a  large  match  emits  about  as  much  light  as  a  burning 


THE  COST  OF  LIGHT  215 

candle  and  a  so-called  safety  match  about  one  third 
as  much. 

A  candle-hour  is  the  total  amount  of  light  emitted 
by  a  standard  candle  in  one  hour,  and  candle-hours  in 
any  case  are  obtained  by  multiplying  the  candle-power 
of  the  source  by  the  hours  of  burning.  In  a  similar 
manner,  lumens  output  multiplied  by  hour's  of  opera¬ 
tion  give  the  lumen-hours.  A  standard  candle  may  be 
considered  to  emit  an  amount  of  light  approximately 
equal  to  10  lumens.  A  wax-candle  will  emit  aTout  as 
much  light  as  a  sperm  candle  but  will  consume  about 
10  per  cent,  less  weight  of  material.  A  tallow  candle 
will  emit  about  the  same  amount  of  light  with  a  con¬ 
sumption  about  50  per  cent,  greater.  The  tallow-can¬ 
dle  has  disappeared  from  use. 

With  the  appearance  of  kerosene  distilled  from  pe¬ 
troleum  the  camphene  lamp  came  into  use.  The  kero¬ 
sene  cost  about  80  cents  per  gallon  during  the  first  few 
years  of  its  introduction.  The  price  of  kerosene  aver¬ 
aged  about  55  cents  a  gallon  between  1865  and  1875. 
During  the  next  decade  it  dropped  to  about  22  cents 
a  gallon  and  between  1885  and  1895  it  sold  as  low  as 
13  cents. 

Artificial  gas  in  1865  sold  approximately  at  $2.50 
per  thousand  cubic  feet;  between  1875  and  1885  at 
$2.00 ;  between  1885  and  1895  at  $1.50. 

The  combined  effect  of  decreasing  cost  of  fuel  or 
electrical  energy  for  light-sources  and  of  the  great  im¬ 
provements  in  light-production  gave  to  the  house¬ 
holder,  for  example,  a  constantly  increasing  amount 
of  light  for  the  same  expenditure.  For  example,  the 


216 


ARTIFICIAL  LIGHT 


family  which  a  century  ago  spent  two  or  three  hours 
in  the  light  of  a  single  candle  now  enjoys  many  times 
more  light  in  the  same  room  for  the  same  price.  It  is 
interesting  to  trace  the  influence  of  this  greatly  dimin¬ 
ishing  cost  of  light  in  the  home.  For  the  sake  of  sim¬ 
plicity  the  light  of  a  candle  will  be  retained  as  the 
unit  and  the  cost  of  light  for  the  home  will  be  con¬ 
sidered  to  remain  approximately  the  same  throughout 
the  period  to  be  considered.  In  fact,  the  amount  of 
money  that  an  average  householder  spends  for  light¬ 
ing  has  remained  fairly  constant  throughout  the  past 
century,  but  he  has  enjoyed  a  longer  period  of  arti¬ 
ficial  light  and  a  greater  amount  of  light  as  the  years 
advanced.  The  following  is  a  table  of  approximate 
values  which  shows  the  lighting  obtainable  for  $20.00 
per  year  throughout  the  past  century  exclusive  of  elec¬ 
tricity  : 


Year 

Hours  per  night 

Equivalent  of 
light  in  candles 

Candle-hours 
per  night  per  year 

1800 

3 

5 

15 

5,500 

1850 

3 

8 

24 

8,700 

1860 

3 

11 

33 

12,000 

1870 

3 

22 

66 

24,000 

1880 

3.5 

36 

126 

46,000 

1890 

4 

50 

200 

73,000 

1900 

5 

154 

770 

280,000 

It  is  seen  from  the  foregoing  that  in  a  century  the 
candle-equivalent  obtainable  for  the  same  cost  to  the 
householder  increased  at  least  thirty  times,  while  the 
hours  during  which  this  light  is  used  has  nearly  dou¬ 
bled.  In  other  words,  in  the  nineteenth  century  the 
candle-hours  obtainable  for  $20.00  per  year  increased 


THE  COST  OF  LIGHT 


217 


about  fifty  times.  Stated  in  another  manner,  the  cost 
of  light  at  the  end  of  the  century  was  about  one  fiftieth 
that  of  candle  light  at  the  beginning  of  the  century. 
One  authority  in  computing  the  expense  of  lighting 
to  the  householder  in  a  large  city  of  this  country  has 
stated  that 

coincident  with  an  increase  of  1700  per  cent,  in  the 
amount  of  night  lighting  of  an  American  family,  in 
average  circumstances,  using  gas  for  light,  there  has 
come  a  reduction  in  the  cost  of  the  year’s  lighting  of 
34  per  cent,  or  approximately  $7.50  per  year;  and 
that  the  cost  of  lighting  per  unit  of  light — the  candle- 
hour — is  now  but  2.8  per  cent,  of  what  it  was  in  the 
first  half  of  the  nineteenth  century.  No  other  neces¬ 
sity  of  household  use  has  been  so  cheapened  and  im¬ 
proved  during  the  last  century. 

In  general,  the  light-user  has  taken  advantage  of  the 
decrease  by  increasing  the  amount  of  light  used  and  the 
period  during  which  it  is  used.  In  this  manner  the 
greatly  diminished  cost  of  light  has  been  a  marked 
sociological  and  economic  influence. 

After  Murdock  made  his  first  installation  of  gas¬ 
lighting  in  an  industrial  plant  early  in  the  nineteenth 
century,  he  published  a  comparison  of  the  expense  of 
operation  with  that  of  candle-lighting.  He  arrived  at 
the  costs  of  light  equivalent  to  1000  candle-hours  as 
follows : 

1000  candle-hours 

Gas-lighting  at  a  rate  of  two  hours  per  day  . . .  $1.95 
“  “  “  “  “  three  “  “  “  ...  1.40 

Candle-lighting  .  6.50 

It  is  seen  that  the  longer  hours  of  burning  reduce  the 


218 


ARTIFICIAL  LIGHT 


cost  of  gas-lighting  by  reducing  the  percentage  of 
overhead  charges.  There  are  no  such  factors  in  light¬ 
ing  by  candles  because  the  whole  ‘ ‘installation ”  is 
consumed.  This  is  an  early  example  of  which  an  au¬ 
thentic  record  is  available.  At  the  present  time  a  cer¬ 
tain  amount  of  light  obtained  for  $1.00  with  efficient 
tungsten  filament  lamps,  costs  $2.00  if  obtained  from 
kerosene  flames  and  about  $50.00  if  obtained  by  burn¬ 
ing  candles. 

In  order  to  obtain  the  cost  of  an  equivalent  amount 
of  light  throughout  the  past  century  a  great  many  fac¬ 
tors  must  be  considered.  Obviously,  the  results  ob¬ 
tained  by  various  persons  will  differ  owing  to  the  un¬ 
avoidable  factor  of  judgment;  h’owever,  the  following 
list  of  approximate  values  will  at  least  indicate  the 
trend  of  the  price  of  light  throughout  the  century  or 
more  of  rapid  developments  in  light-production.  A 
fair  average  of  the  retail  values  of  fuels  and  of  elec¬ 
trical  energy  and  an  average  luminous  efficiency  of  the 
light-sources  involved  have  been  used  in  making  the 
computations.  The  figures  apply  particularly  to  this 
country. 

Table  Showinc  the  Approximate  Total  Cost  of 
1000  Candle-Hours  for  Various  Periods 

Per  1000 
candle-hours 


1800  to  1850,  sperm-oil  .  $2.40 

tallow  candle  .  5.00 

1850  to  1865,  kerosene  .  1.65 

tallow  candle .  6.85 

1865  to  1875,  kerosene . 75 

tallow  candle  .  6.25 

gas,  open-flame . 90 


THE  COST  OF  LIGHT 


219 


Per  1000 
eandle-hours 


1875  to  1885,  kerosene  . 25 

gas,  open-flame . 60 

1885  to  1895,  kerosene  . 15 

gas,  open-flame . 40 

1895  to  1915,  gas  mantle . 07 

carbon  filament . 38 

metallized  filament . 28 


tungsten  filament  (vacuum)  ...  .12 
tungsten  filament  (gas-filled)  . .  .07 

In  these  days  the  cost  of  living  has  claimed  consid¬ 
erable  attention  and  it  is  interesting  to  compare  that 
of  lighting.  In  the  following  table  the  price  of  food 
and  of  electric  lighting  are  compared  for  twenty  years 
preceding  the  recent  war.  The  great  disturbance  due 
to  the  war  is  thereby  eliminated  from  consideration, 
but  it  should  be  noted  that  since  1914  the  price  of  food 
has  greatly  increased  but  that  of  electric  lighting  has 
not  changed  materially.  The  cost  of  each  commodity 
is  taken  as  one  hundred  units  for  the  year  1894  but,  of 
course,  the  actual  cost  of  living  for  the  householder  is 
perhaps  a  hundred  times  greater  than  the  cost  of  elec- 


trie  lighting. 

Year 

Food 

Electric  light 

1894 

100 

100 

1896 

80 

92 

1898 

92 

90 

1900 

100 

85 

1902 

113 

77 

1904 

110 

77 

1906 

115 

57 

220 


ARTIFICIAL  LIGHT 


Year 

Food 

Electric  ligl 

1908 

128 

• 

30 

1910 

138 

28 

1912 

144 

23 

1914 

145 

17 

One  feature  of  electric  lighting  which  puzzles  the 
consumer  and  which  gives  the  politicians  an  oppor¬ 
tunity  for  crying  “discrimination”  and  “injustice”  at 
the  public-service  company  is  the  great  variation  in 
rates.  There  is  no  discrimination  or  injustice  when 
the  householder,  for  example,  must  pay  more  for  his 
lighting  than  a  factory  pays.  The  rates  are  not  only 
affected  by  “demand”  but  by  the  period  in  which  the 
demand  comes.  Residence  lighting  is  chiefly  confined 
to  certain  hours  from  5  to  9  p.  m.  and  there  is  a  great 
“peak”  of  demand  at  this  time.  The  central-stations 
must  have  equipment  available  for  this  short-time  de¬ 
mand  and  much  of  the  capacity  of  the  equipment  is 
unused  during  the  remainder  of  the  day.  The  factory 
which  uses  electricity  throughout  the  day  or  night  or 
both  is  helping  to  keep  the  central-station  operating 
efficiently.  The  equipment  necessary  to  supply  elec¬ 
tricity  to  the  factory  is  operating  long  hours.  Not 
only  is  this  overhead  charge  much  less  for  factories 
and  many  other  consumers  than  for  the  householder, 
but  the  expense  of  accounting,  of  reading  meters,  etc., 
is  about  the  same  for  all  classes  of  consumers.  There¬ 
fore,  this  is  an  appreciable  item  on  the  bill  of  the  small 
consumer. 

Doubtless,  the  public  does  not  realize  that  the  enor¬ 
mous  decrease  in  the  cost  of  lighting  during  the  past 
century  is  due  largely  to  the  fact  that  the  lighting  in- 


THE  COST  OF  LIGHT 


221 


dustry  has  grown  large.  Increased  production  is  re¬ 
sponsible  for  some  of  this  decrease  and  science  for 
much  of  it.  The  latter,  having  been  called  to  the  aid 
of  the  manufacturers,  who  are  better  able  by  virtue 
of  their  magnitude  to  spend  time  and  resources  upon 
scientific  developments,  has  responded  with  many  im¬ 
provements  which  have  increased  the  efficiency  of  light- 
production.  Some  figures  of  the  Census  Bureau  may 
be  of  interest.  These  are  given  for  1914  in  order  that 
the  abnormal  conditions  due  to  the  recent  war  may 
be  avoided.  The  figures  pertaining  to  the  manu¬ 
facture  of  gas  for  sale  which  do  not  include  private 
plants  are  as  follows  for  the  year  1914  for  this 
country : 


Number  of  establishments .  1,284 

Capital  .  $1,252,421,584 

Value  of  products  (gas,  coke,  tar,  etc.)  $220,237,790 

Cost  of  materials  .  $76,779,288 

Value  added  by  manufacture .  $143,458,502 

Value  of  gas  .  $175,065,920 

Coal  used  (tons)  .  6,116,672 

Coke  used  (tons)  .  964,851 

Oil  used  (gallons)  .  715,418,623 

Length  of  gas  mains  (miles)  .  58,727 

Manufactured  products  sold 

Total  gas  (cubic  feet)  . 203,639,260,000 

Straight  coal  gas  (cubic  feet)  .  10,509,946,000 

Carbureted  water  gas  (cubic  feet)  . . .  90,017,725,000 
Mixed  coal-  and  water-gas  (cubic  feet)  86,281,339,000 

Oil  gas  (cubic  feet)  .  16,512,274,000 

Acetylene  (cubic  feet)  .  136,564,000 

Other  gas,  chiefly  gasolene  (cubic  feet)  181,412,000 
Coke  (bushels)  .  114,091,753 


222 


ARTIFICIAL  LIGHT 


Tar  (gallons)  .  125,938,607 

Ammonia  liquors  (gallons)  .  50,737,762 

Ammonia,  sulphate  (pounds)  .  6,216,618 


Of  course,  only  a  small  fraction  of  the  total  gas  manu¬ 
factured  is  used  for  lighting. 

According  to  the  U.  S.  Geological  Survey,  the  quan¬ 
tities  of  gas  sold  in  this  country  in  the  year  1917  were 
as  follows: 


Coal-gas  .  42,927,728,000  cubic  feet 

Water-gas .  153,457,318,000  “  “ 

Oil-gas .  14,739,508,000  “  “ 


Byproduct  gas  ..  131,026,575,000  “  “ 

Natural  gas  ....  795,110,376,000  “  “ 

In  1914  there  were  38,705,496  barrels  (each  fifty  gal¬ 
lons)  of  illuminating  oils  refined  in  this  country  and 
the  value  was  $96,806,452.  About  half  of  this  quantity 
was  exported.  In  1914  the  value  of  all  candles  manu¬ 
factured  in  this  country  was  about  $2,000,000,  which 
was  about  half  that  of  the  candles  manufactured  in 
1909  and  in  1904.  In  1914  the  value  of  the  matches 
manufactured  in  this  country  was  $12,556,000.  This 
has  increased  steadily  from  $429,000  in  1849.  In  1914 
the  glass  industries  in  this  country  made  7,000,000 
lamps,  70,000,000  chimneys,  16,300,000  lantern  globes, 
24,000,000  shades,  globes,  and  other  gas  goods.  Many 
millions  of  other  lighting  accessories  were  made,  but 
unfortunately  they  are  not  classified. 

Some  figures  pertaining  to  public  electric  light  and 
power  stations  of  the  United  States  for  the  years  1907 
and  1917  are  as  follows : 


THE  COST  OF  LIGHT 


223 


Number  of  establishments . 

Commercial  . 

Municipal  . 

Income  . 

Total  horse-power  of  plants . 

Steam  engines  . 

Internal  combustion  engines  . .  . 

Water-wheels  . 

Kilowatt  capacity  of  generators  .  . . 
Output  in  millions  of  kilowatt-hours 

Motors  served  (horse-power)  . 

Electric-arc  street-lamps  served .... 
Electric-filament  street-lamps  served 


1917 

1907 

6,541 

4,714 

4,224 

3,462 

2,317 

1,562 

$526,886,408 

$175,642,338 

12,857,998 

4,098,188 

8,389,380 

2,693,273 

217,186 

55,828 

4,251,423 

1,349,087 

9,001,872 

2,709,225 

25,438 

5,863 

9,216,323 

1,649,026 

256,838 

1,389,382 

In  general,  there  is  a  large  increase  in  the  various 
items  during  the  decade  represented.  The  output  of 
the  central  stations  doubled  in  the  five  years  from 
1907  to  1912,  and  doubled  again  in  the  next  five  years 
from  1912  to  1917.  Street  lamps  were  not  reported 
in  1907,  but  in  1912  there  were  348,643  arc-lamps 
served  by  the  public  companies.  The  number  of  arc- 
lamps  decreased  to  256,838  in  1917.  On  the  other  hand, 
there  were  681,957  electric  filament  street  lamps  served 
in  1912,  which  doubled  in  number  to  1,389,382  in  1917. 
The  cost  of  construction  and  equipment  of  these  cen¬ 
tral  stations  totaled  more  than  $3,000,000,000  in  1917. 

Although  there  is  no  immediate  prospect  of  the  fail¬ 
ure  of  the  coal  and  oil  supplies,  exhaustion  is  surely 
approaching.  And  as  the  supplies  of  fuel  for  the 
production  of  gas  and  electricity  diminish,  the  cost 
of  lighting  may  advance.  The  total  amount  of  oil 
available  in  the  known  oil-fields  of  this  country  at  the 
present  time  has  been  estimated  by  various  experts 
between  5,000,000,000  and  20,000,000,000  barrels,  the 
best  estimate  being  about  7,000,000,000.  The  annual 
consumption  is  now  about  400,000,000  barrels.  These 


224  ‘ 


ARTIFICIAL  LIGHT 


figures  do  not  take  into  account  the  oil  which  may  be 
distilled  from  the  rich  shale  deposits.  Apparently 
this  source  will  yield  a  hundred  billion  barrels  of  oil. 
In  a  similar  manner  the  coal-supply  is  diminishing 
and  the  consumption  is  increasing.  In  1918  more  than 
a  half-billion  tons  of  coal  were  shipped  from  the  mines. 
The  production  of  natural  gas  perhaps  has  reached 
its  peak,  and,  owing  to  its  relation  to  the  coal  and  oil 
deposits,  its  supply  is  limited. 

Although  only  a  fraction  of  the  total  production  of 
gas,  oil,  and  coal  is  used  in  lighting,  the  limited  supply 
of  these  products  emphasizes  the  desirability  of  de¬ 
veloping  the  enormous  water-power  resources  of  this 
country.  The  present  generation  will  not  be  hard 
pressed  by  the  diminution  of  the  supply  of  gas,  oil, 
and  coal,  but  it  can  profit  by  encouraging  and  even 
demanding  the  development  of  water-power.  Further¬ 
more,  it  is  an  obligation  to  succeeding  generations  to 
harness  the  rivers  and  even  the  tides  and  waves  in 
order  that  the  other  resources  will  be  conserved  as  long 
as  possible.  Science  will  continue  to  produce  more  effi¬ 
cient  light-sources,  but  the  cost  of  light  finally  is  de¬ 
pendent  upon  the  cost  of  the  energy  supplied  to  these 
lamps.  At  the  present  time  water-power  is  the  anchor 
to  the  windward. 


XVII 

LIGHT  AND  SAFETY 

It  is  established  that  outdoors  life  and  property  are 
at  night  safer  under  adequate  lighting  than  they  are 
under  inadequate  lighting.  Police  departments  in  the 
large  cities  will  testify  that  street-lighting  is  a  power¬ 
ful  ally  and  that  crime  is  fostered  by  darkness.  But 
in  reckoning  the  cost  of  street-lighting  to-day  how 
many  take  into  account  the  value  of  safety  to  life  and 
property  and  the  saving  occasioned  by  the  reduction 
in  the  police-force  necessary  to  patrol  the  cities  and 
towns?  Owing  to  the  necessity  of  darkening  the 
streets  in  order  to  reduce  the  hazards  of  air-raids,  Lon¬ 
don  experienced  a  great  increase  in  accidents  on  the 
streets,  which  demonstrated  the  practical  value  of 
street-lighting  from  the  standpoint  of  accident  preven¬ 
tion. 

During  the  war,  when  dastardly  traitors  and  agents 
of  the  enemy  were  striking  at  industry,  the  value  of 
lighting  was  further  recognized  by  the  industries,  with 
the  result  that  flood-lighting  was  installed  to  protect 
them.  By  common  consent  this  new  phase  was  termed 
“ protective  lighting.”  Soon  after  the  entrance  of  this 
country  into  the  recent  war,  the  U.  S.  Military  Intelli¬ 
gence  established  a  Section  of  Plant  Protection  which 
had  thirty-three  district  offices  during  the  war  and 
gave  attention  to  thirty-five  thousand  industrial  plants 

225 


226 


ARTIFICIAL  LIGHT 


engaged  in  production  of  war  materials.  Protective 
lighting  was  early  recognized  by  this  section  as  a  very 
potential  agency  for  defense,  and  extensive  use  was 
made  of  it.  For  example,  Edmund  Leigh,  chief  of  the 
section,  in  discussing  the  value  of  outdoor  lighting 
stated : 

An  illustration  of  our  work  in  this  connection  is  the 
case  of  an  $80,000,000  powder  plant  of  recent  construc¬ 
tion.  We  arranged  to  have  all  wires  buried.  In  ad¬ 
dition  to  the  ordinary  lighting  on  an  adjacent  hill 
there  is  a  large  searchlight  which  will  command  any 
part  of  the  buildings  and  grounds.  Every  three  hun¬ 
dred  yards  there  is  a  watch-tower  with  a  searchlight 
on  top.  These  searchlights  are  for  use  only  in  emer¬ 
gency.  Each  tower  has  a  telephone  service,  one  con¬ 
nected  with  the  other.  The  men  in  the  towers  have  a 
view  of  the  building  exteriors,  which  are  all  well 
lighted,  and  the  men  in  the  buildings  look  across  the 
yard  to  the  lighted  fence  line  and  so  get  a  silhouette 
of  persons  or  objects  in  between.  The  most  vital  parts 
of  the  buildings  are  surrounded  by  three  fences.  In 
the  near-by  woods  the  underbrush  has  been  cleared 
out  and  destroyed.  The  trunks  and  limbs  of  trees 
have  been  whitewashed.  No  one  can  walk  among  these 
trees  or  between  the  trees  and  the  plant  without  being 
seen  in  silhouette.  ...  I  say  flatly  that  I  know  noth¬ 
ing  that  is  so  potential  for  good  defense  as  good 
illumination  and  at  the  same  time  so  little  understood. 

Without  such  protective  lighting  an  army  of  men  would 
have  been  required  to  insure  the  safety  of  this  one 
vital  plant;  still  it  is  obvious  that  the  cost  of  the 
protective  lighting  was  an  insignificant  part  of  the 
value  of  the  plant  which  it  insured  against  damage  and 
destruction. 


LIGHT  AND  SAFETY 


227 


The  United  States  participated  for  nineteen  months 
in  the  recent  war  and  during  that  time  about  400,000 
casualties  were  suffered  by  its  forces.  This  was  at 
the  rate  of  about  250,000  per  year,  which  included  cas¬ 
ualties  in  battle,  at  sea,  and  from  sickness,  wounds,  and 
accidents.  Every  one  has  felt  the  magnitude  of  this 
rate  of  casualties  because  either  his  home  or  that  of  a 
friend  was  blighted  by  one  or  more  of  these  tragedies 
in  the  nineteen  months.  However,  R.  E.  Simpson  of 
the  Travelers  Insurance  Company  has  stated  that: 

During  a  one-year  period  in  this  country  the  number 
of  accidents  due  to  inadequate  or  improper  lighting 
exceeds  the  yearly  rate  of  our  war  casualties. 

This  is  a  startling  comparison,  which  emphasizes  a 
phase  of  lighting  that  has  long  been  recognized  by  ex¬ 
perts  but  has  been  generally  ignored  by  the  industries 
and  by  the  public.  The  condition  doubtless  is  due 
largely  to  a  lag  in  the  proper  utilization  of  artificial 
lighting  behind  the  rapid  increase  in  congestion  in  the 
industries  and  in  public  places. 

Accident  prevention  is  an  important  phase  of  mod¬ 
ern  life  which  must  receive  more  attention.  From 
published  statistics  and  conservative  estimates  it  has 
been  concluded  that  there  are  approximately  25,000 
persons  killed  or  permanently  disabled,  500,000  se¬ 
riously  injured,  and  1,000,000  slightly  injured  each 
year  in  this  country.  Translating  these  figures  by 
means  of  the  accident  severity  rates,  Mr.  Simpson  has 
found  that  there  is  a  total  of  180,000,000  days  of  time 
lost  per  year.  This  is  equivalent  to  the  loss  of  serv¬ 
ices  of  600,000  men  for  a  full  year  of  300  work-days. 


228 


ARTIFICIAL  LIGHT 


This  loss  is  distributed  over  the  entire  country  and 
consequently  its  magnitude  is  not  demonstrated  ex¬ 
cepting  by  statistics.  Of  course,  the  causes  of  the  ac¬ 
cidents  are  numerous,  but,  among  the  means  of  pre¬ 
vention,  proper  lighting  is  important. 

According  to  some  authorities  at  least  18  per  cent, 
of  these  accidents  are  due  to  defects  in  lighting.  On 
this  basis  the  services  of  108,000  men  as  producers  and 
wage-earners  are  continually  lost  at  the  present  time 
because  the  lighting  is  not  sufficient  or  proper  for  the 
safety  of  workers.  If  the  full  year’s  labor  of  108,- 
000  men  could  be  applied  to  the  mining  of  coal,  130,- 
000,000  million  tons  of  coal  would  be  added  to  the 
yearly  output;  and  only  10,000  tons  would  be  neces¬ 
sary  to  supply  adequate  lighting  for  this  army  of  men 
working  for  a  full  year  for  ten  hours  each  day. 

Statistics  obtained  under  the  British  workmen’s  com¬ 
pensation  system  show  that  25  per  cent,  of  the  acci¬ 
dents  were  caused  by  inadequate  lighting  of  industrial 
plants. 

Much  has  been  said  and  actually  done  regarding  the 
saving  of  fuel  by  curtailing  lighting,  but  the  saving 
may  easily  be  converted  into  a  great  loss.  For  ex¬ 
ample,  a  25-watt  electric  lamp  may  be  operated  ten 
hours  a  day  for  a  whole  year  at  the  expense  of  one 
eighth  of  a  ton  of  coal.  Suppose  this  lamp  to  be  over 
a  stairway  or  at  any  vital  point  and  that  by  extinguish¬ 
ing  it  there  occurs  a  single  accident  which  involves  the 
loss  of  only  one  day’s  work  on  the  part  of  the  worker. 
If  this  one  day’s  time  could  have  produced  coal,  there 
would  have  been  enough  coal  mined  in  the  ten  hours  to 
operate  the  lamp  for  thirty-two  years.  The  insignifi- 


LIGHT  AND  SAFETY 


229 


cant  cost  of  lighting  is  also  shown  by  the  distribution 
of  the  consumption  of  fuel  for  heating,  cooking,  and 
lighting  in  the  home.  Of  the  total  amount  of  fuel  con¬ 
sumed  in  the  home  for  these  purposes,  87  per  cent,  is 
for  heating,  11  per  cent,  for  cooking  and  2  per  cent,  for 
lighting.  The  amount  of  coal  used  for  lighting  pur¬ 
poses  in  general  is  about  2.5  per  cent,  of  the  total  con¬ 
sumption  of  coal,  so  it  is  seen  that  the  curtailment  of 
lighting  at  best  cannot  save  much  fuel;  and  it  may  ac¬ 
tually  result  in  a  great  economic  loss.  By  replacing  in¬ 
efficient  lamps  and  accessories  with  efficient  lighting- 
equipment  and  by  washing  windows  and  artificial 
lighting  devices,  a  real  saving  can  be  realized. 

Improper  lighting  may  be  as  productive  of  accidents 
as  inadequate  lighting,  and  throughout  the  industries 
and  upon  the  streets  the  misuse  of  light  is  in  evidence. 
The  blinding  effect  of  a  brilliant  light-source  is  easily 
proved  by  looking  at  the  sun.  After  a  few  moments 
great  discomfort  is  experienced,  and  on  looking  away 
from  this  brilliant  source  the  eyes  are  temporarily 
blinded  by  the  after-images.  When  this  happens  in  a 
factory  as  the  result  of  gazing  into  an  unshielded  light- 
source,  the  workman  may  be  injured  by  moving  ma¬ 
chinery,  by  stumbling  over  objects,  and  in  many  other 
ways.  Unshaded  light-sources  are  too  prevalent  in 
the  industries.  Improper  lighting  is  likely  to  cause 
deep  shadows  wherein  many  dangers  may  be  hidden. 
On  the  street  the  glare  from  automobile  head-lamps  is 
very  prevalent  and  nearly  everybody  may  testify  from 
experience  to  the  dangers  of  glare.  Even  the  glaring 
locomotive  head-lamp  has  been  responsible  for  many 
casualties. 


230 


ARTIFICIAL  LIGHT 


Unfortunately,  natural  lighting  outdoors  has  not 
been  under  the  control  of  man  and  he  has  accepted  it 
as  it  is.  The  sky  is  a  harmless  source  of  light  when 
viewed  outdoors  and  the  sun  is  in  such  a  position  that 
it  is  usually  easy  to  avoid  looking  at  it.  It  is  so  in¬ 
tensely  glaring  that  man  unconsciously  avoids  look¬ 
ing  directly  at  it.  These  conditions  are  responsible 
to  an  extent  for  man’s  indifference  and  even  ignorance 
of  the  rudiments  of  safe  lighting.  When  he  has  arti¬ 
ficial  light,  over  which  he  may  exercise  control,  he 
either  ignores  it  or  owing  to  the  less  striking  glare  he 
misuses  it  and  his  eyesight  without  realizing  it.  A 
great  deal  of  eye-strain  and  permanent  eye  trouble 
arises  from  the  abuse  of  the  eyes  by  improper  light¬ 
ing.  For  example,  near-sightedness  is  often  due  to 
inadequate  illumination,  which  makes  it  necessary  for 
the  eyes  to  he  near  the  work  or  the  reading-page.  Im¬ 
proper  or  inadequate  lighting  especially  influences  eyes 
that  are  immature  in  growth  and  in  function,  and  it 
has  been  shown  that  with  improvements  in  lighting 
the  percentage  of  short-sightedness  has  decreased  in 
the  schools.  Furthermore,  it  has  been  shown  that 
where  no  particular  attention  has  been  given  to  light¬ 
ing  and  vision,  the  percentage  of  short-sightedness  has 
increased  with  the  grade.  There  are  twenty  million 
school  children  in  this  country  whose  future  eyesight 
is  in  the  hands  of  those  who  have  jurisdiction  over 
lighting  and  vision.  There  are  more  than  a  hundred 
million  persons  in  this  country  whose  eyes  are  daily 
subjected  to  improper  lighting-conditions,  either 
through  this  own  indifference  or  through  the  negli¬ 
gence  of  others. 


231 


LIGHT  AND  SAFETY 

Of  a  certain  group  of  91,000  purely  industrial  acci¬ 
dents  in  the  year  1910,  Mr.  Simpson  has  stated  that 
23.8  per  cent,  were  due,  directly  or  indirectly,  to  the 
lack  of  proper  illumination.  These  may  he  further  di¬ 
vided  into  two  approximately  equal  groups,  one  of 
which  comprises  the  accidents  due  to  inadequate  illum¬ 
ination  and  the  other  to  those  toward  which  improper 
lighting  was  a  contributing  cause.  The  seasonal  varia¬ 
tion  of  these  accidents  is  given  in  the  following  table, 
both  for  those  due  directly  or  indirectly  to  inadequate 
and  improper  lighting  and  those  due  to  other  causes. 

Seasonal  Distribution  of  Industrial  Accidents  Due  to 
Lighting  Conditions  and  to  Other  Causes 

Percentage  due  to 
Lighting  conditions  Other  causes 


J uly  . 

.  4.8 

5.9 

August  . 

.  5.2 

6.2 

September  . 

.  6.1 

6.9 

October  . 

.  8.6 

8.5 

November  . 

.  10.9 

10.5 

December  . 

.  15.6 

12.2 

January  . 

.  16.1 

11.9 

February  . 

.  10.0 

10.5 

March  . 

.  7.6 

8.8 

April  . 

.  6.1 

6.9 

May  . 

.  5.2 

5.8 

June . 

.  3.8 

5.9 

The  figures  in  one  column  have  no  direct  relation  to 
those  in  the  other;  that  is,  each  column  must  be  con¬ 
sidered  by  itself.  It  is  seen  from  the  foregoing  that 
about  half  the  number  of  the  accidents  due  to  poor 
illumination  occurred  in  the  months  of  November,  De- 


232 


ARTIFICIAL  LIGHT 


cember,  January,  and  February.  These  are  the 
months  of  inadequate  illumination  unless  artificial 
lighting  has  been  given  special  attention.  The  same 
general  type  of  seasonal  distribution  of  accidents  due 
to  other  causes  is  seen  to  exist  but  not  so  prominently. 
The  greatest  monthly  rate  of  accidents  during  the  win¬ 
ter  season  is  nearly  four  times  the  minimum  monthly 
rate  during  the  summer  for  those  accidents  due  to 
lighting  conditions.  This  ratio  reduces  to  about  twice 
in  the  case  of  accidents  due  to  other  causes.  Looking 
at  the  data  from  another  angle,  it  may  be  considered 
that  the  likelihood  of  an  accident  being  caused  by  light¬ 
ing  conditions  is  about  twice  as  great  in  any  of  the 
four  4 ‘winter”  months  as  in  any  of  the  remaining 
eight  months.  Doubtless,  this  may  be  explained 
largely  upon  the  basis  of  morale.  The  winter  months 
are  more  dreary  than  those  of  summer  and  the  work¬ 
man’s  general  outlook  is  different  in  winter  than  in 
summer.  In  the  former  season  he  goes  back  and  forth 
to  work  in  the  dark,  or  at  best,  in  the  cold  twilight. 
He  is  not  only  more  depressed  but  he  is  clumsier  in 
his  heavier  clothing.  If  the  enervating  influence  of 
these  factors  is  combined  with  a  greater  clumsiness 
due  to  cold  and  perhaps  to  colds,  it  is  not  difficult  to 
account  for  this  type  of  seasonal  distribution  of  acci¬ 
dents.  A  study  of  the  accidents  of  1917  indicated  that 
13  per  cent,  occurred  between  5  and  6  p.  m.  when  arti¬ 
ficial  lighting  is  generally  in  use  to  help  out  the  fail¬ 
ing  daylight.  Only  7.3  per  cent,  occurred  between  12 
m.  and  1  p.  m. 

There  is  another  aspect  of  the  subject  which  deals 
particularly  with  the  safety  of  the'  light-source  or 


SIGNAL-LIGHT  FOR  AIRPLANE 


TRENCH  LIGHT-SIGNALING  OUTFIT 


r 


n 


AVIATION  FIELD  LIGHT-  SIGNAL  SEARCH-LIGHT  FOR  AIRPLANE 

SIGNAL  PROJECTOR 


UNSAFE,  UNPRODUCTIVE  LIGHTING  WORTHY  OF  THE  DARK  AGES 


THE  SAME  FACTORY  MADE  SAFE,  CHEERFUL,  AND  MORE  PRODUCTIVE  BY 

MODERN  LIGHTING 


LIGHT  AND  SAFETY 


233 


method  of  lighting.  As  each  innovation  in  lighting 
appeared  during  the  past  century  there  immediately 
arose  the  question  of  safety.  The  fire-hazard  of  open 
flames  received  attention  in  early  days,  and  when  gas¬ 
lighting  appeared  it  was  condemned  as  a  poison  and 
an  explosive.  Mineral-oil  lamps  introduced  the  dan¬ 
ger  of  explosions  of  the  vapors  produced  by  evapora¬ 
tion.  When  electric  lighting  appeared  it  was  investi¬ 
gated  thoroughly.  The  result  of  all  this  has  been  an 
effort  to  make  lamps  and  methods  safe.  Insurance 
companies  have  the  relative  safety  of  these  systems 
established  to  their  satisfaction  and  to-day  little  fire- 
hazard  is  attached  to  the  present  modes  of  general 
lighting  if  proper  precautions  have  been  taken. 

When  electric  lighting  was  first  introduced  the  pub¬ 
lic  looked  upon  electricity  as  dangerous  and  naturally 
many  questions  pertaining  to  hazards  arose.  The  dis¬ 
tribution  of  electricity  has  been  so  highly  perfected 
that  little  is  heard  of  the  hazards  which  were  so  mag¬ 
nified  in  the  early  years.  Data  gathered  between  1884 
and  1889  showed  that  about  13,000  fires  took  place  in 
a  certain  district.  Of  these,  42  were  attributed  to  elec¬ 
tric  wires;  22  times  as  many  to  breakage  and  explosion 
of  kerosene  lamps;  and  ten  times  as  many  through 
carelessness  with  matches.  These  figures  cannot  be 
taken  at  their  face  value  because  of  the  absence  of 
data  showing  the  relative  amount  of  electric  and  kero¬ 
sene  lighting;  nevertheless  they  are  interesting  because 
they  represent  the  early  period. 

There  are  industries  where  unusual  care  must  be  ex¬ 
ercised  in  regard  to  the  lighting.  In  certain  chemical 
industries  no  lamps  are  used  excepting  the  incandes- 


234 


ARTIFICIAL  LIGHT 


cent  lamp  and  this  is  enclosed  in  an  air-tight  glass 
globe.  Even  a  public-service  gas  company  cautions 
its  employees  and  patrons  thus:  Do  not  look  for  a 
gas-leak  with  a  naked  light!  Use  electric  light.” 
The  coal-mine  offers  an  interesting  example  of  the  pre¬ 
cautions  necessary  because  the  same  type  of  problems 
are  found  in  it  as  in  industries  in  general,  with  the 
additional  difficulties  attending  the  presence  or  possi¬ 
ble  presence  of  explosive  gas.  The  surroundings  in  a 
coal-mine  reflect  a  small  percentage  of  the  light,  so 
that  much  light  is  wasted  unless  the  walls  are  white¬ 
washed.  This  is  a  practical  method  for  increasing 
safety  in  coal-mines.  However,  the  most  dangerous 
feature  is  the  light-source  itself.  According  to  the 
Bureau  of  Mines  during  the  years  1916  and  1917  about 
60  per  cent,  of  the  fatalities  due  to  gas  and  coal-dust 
explosions  were  directly  traceable  to  the  use  of  defec¬ 
tive  safety  lamps  and  to  open  flames. 

In  the  early  days  of  coal-mining  it  was  found  that 
the  flame  of  a  candle  occasionally  caused  explosions  in 
the  mines.  It  was  also  found  that  sparks  of  flint  and 
steel  would  not  readily  ignite  the  gas  or  coal-dust  and 
this  primitive  device  was  used  as  a  light-source.  Of 
course,  statistics  are  unavailable  concerning  the  cas¬ 
ualties  in  coal-mines  throughout  the  past  centuries,  but 
with  the  accidents  not  uncommon  in  this  scientific  age, 
with  its  elaborate  organizations  striving  to  stamp  out 
such  casualties,  there  is  good  reason  to  believe  that 
previous  to  a  century  or  two  ago  the  risks  of  coal¬ 
mining  must  have  been  great.  Open  flames  have  been 
widely  used  in  this  industry,  but  there  has  always  been 


LIGHT  AND  SAFETY  235 

the  risk  of  the  presence  or  the  appearance  of  gas  or 
explosive  dust. 

The  early  open-flame  lamps  not  only  were  sources  of 
danger  but  their  feeble  varying  intensity  caused  se¬ 
rious  damage  to  the  eyesight  of  miners.  This  factor 
is  always  present  in  inadequate  and  improper  lighting, 
but  its  influence  is  noticeable  in  coal-mining  in  the 
nervous  disease  affecting  the  eyes  which  is  known  as 
nystagmus.  The  symptoms  of  the  disease  are  inability 
to  see  at  night  and  the  dazzling  effect  of  ordinary 
lamps.  Finally  objects  appear  to  the  sufferer  to  dance 
about  and  his  vision  is  generally  very  much  disturbed. 

The  oil-lamps  used  in  coal-mining  have  a  luminous 
intensity  equivalent  to  about  one  to  four  candles,  hut 
owing  to  the  atmospheric  conditions  in  the  mines  a 
flame  does  not  burn  as  brightly  as  in  the  fresh  air. 
The  possibility  of  explosion  due  to  the  open  flame  was 
eliminated  by  surrounding  it  with  a  metal  gauze. 
Davy  was  the  inventor  of  this  device  and  his  safety 
lamp  introduced  about  a  hundred  years  ago  has  been 
a  boon  to  the  coal-miner.  Various  improvements  have 
been  devised,  but  Davy’s  lamp  contained  the  essentials 
of  a  safety  device.  The  flame  is  surrounded  by  a 
cylinder  of  metal  gauze  which  by  forming  a  much 
cooler  boundary  prevents  the  mine-gas  from  becoming 
heated  locally  by  the  lamp  flame  to  a  sufficient  tempera¬ 
ture  to  ignite  and  consequently  to  explode.  This  de¬ 
vice  not  only  keeps  the  flame  from  igniting  the  gas 
but  it  also  serves  as  an  indicator  of  the  amount  of  gas 
present,  by  the  variation  in  the  size  and  appearance 
of  the  tip  of  the  flame.  However,  the  gauze  reduces 


236  * 


ARTIFICIAL  LIGHT 


the  luminous  output,  and  as  it  accumulates  soot  and 
dust  the  light  is  greatly  diminished.  One  of  these 
lamps  is  about  as  luminous  as  a  candle,  initially,  but 
its  intensity  is  often  reduced  by  accumulations  upon 
the  gauze  to  only  one  fifth  of  the  initial  value. 

The  acetylene  lamp  is  the  best  open-flame  light- 
source  available  to  the  miner,  for  several  reasons.  It 
is  of  a  higher  candle-power  than  the  others  and  as  it  is 
a  burning  gas,  there  is  not  the  danger  of  flying  sparks 
as  in  the  case  of  burning  wicks.  The  greater  inten¬ 
sity  of  illumination  affords  a  greater  safety  to  the 
miner  by  enabling  him  to  detect  loose  rock  which  may 
be  ready  to  fall  upon  him.  However,  this  lamp  may 
be  a  source  of  danger,  owing  to  the  fact  that  it  will 
burn  more  brilliantly  in  a  vitiated  atmosphere  than 
other  flame-lamps.  Another  disadvantage  is  the  pos¬ 
sibility  of  calcium  carbide  accidentally  spilt  coming 
in  contact  with  water  and  thereby  causing  the  genera¬ 
tion  of  acetylene  gas.  If  this  is  produced  in  the  mine 
in  sufficient  quantities  it  is  a  danger  which  may  not 
be  suspected.  If  ignited  it  will  explode  and  may  also 
cause  severe  burns. 

The  electric  lamp,  being  an  enclosed  light-source 
capable  of  being  subdivided  and  fed  by  a  small  portable 
battery,  early  gave  promise  of  solving  the  problem  of 
a  safe  mine-lamp  of  adequate  candle-power.  Much 
ingenuity  has  been  applied  to  the  development  of  a 
portable  electric  safety  mine-lamp,  and  several  such 
lamps  are  now  approved  by  the  Bureau  of  Mines. 
Two  general  types  are  being  manufactured,  the  cap 
outfit  and  the  hand  outfit.  They  consist  essentially  of 
a  lamp  in  a  reflector  whose  aperture  is  closed  with  a 


LIGHT  AND  SAFETY 


237 


sheet  or  a  lens  of  clear  glass.  The  battery  may  be  of 
the  “dry”  or  “storage”  type  and  in  the  case  of  the 
cap  outfit  the  battery  is  carried  on  the  back.  The 
specifications  for  these  lamps  demand  that  a  luminous 
intensity  averaging  at  least  0.4  candle  be  maintained 
throughout  twelve  consecutive  hours  of  operation.  At 
no  time  during  this  period  shall  the  output  of  light 
fall  below  1.25  lumens  for  a  cap-lamp  and  below  3 
lumens  for  a  hand-lamp.  Inasmuch  as  these  are 
equipped  with  reflectors,  the  specifications  insist  that 
a  circle  of  light  at  least  seven  feet  in  diameter  shall 
be  cast  on  a  wall  twenty  inches  away.  It  appears  that 
a  portable  lamp  is  an  economic  necessity  in  the  coal¬ 
mines,  on  account  of  the  expense,  inconvenience,  and 
possible  dangers  introduced  by  distribution  systems 
such  as  are  used  in  most  places. 

Although  the  major  defects  in  lighting  are  due  to 
absence  of  light  in  dangerous  places,  to  glare,  and  to 
other  factors  of  improper  lighting,  there  are  many 
minor  details  which  may  contribute  to  safety.  For 
example,  low  lamps  are  useful  in  making  steps  in 
theaters  and  in  other  places,  in  drawing  attention  to 
the  entrances  of  elevators,  in  lighting  the  aisles  of 
Pullman  cars,  under  hand-rails  on  stairways,  and  in 
many  other  vital  places.  A  study  of  accidents  indi¬ 
cates  that  simple  expedients  are  effective  preventives. 


XVIII 

THE  COST  OF  LIVING 

A  comparison  of  the  civilization  of  the  present  with 
that  of  a  century  ago  reveals  a  startling  difference  in 
the  standards  of  living.  To-day  mankind  enjoys  con¬ 
veniences  and  luxuries  that  were  undreamed  of  by  the 
past  generations.  For  example,  a  certain  town  in 
Iowa,  a  score  of  years  ago,  was  appraised  for  a  bond- 
issue  and  it  was  necessary  to  extend  its  limits  con¬ 
siderably  in  order  to  include  a  valuation  of  one  half 
million  dollars  required  by  the  underwriters.  On  a 
summer’s  evening  at  the  present  time  a  thousand 
“ pleasure”  automobiles  may  be  found  parked  along 
its  streets  and  these  exceed  in  valuation  that  of  the 
entire  town  only  twenty  years  ago  and  equal  it  to¬ 
day.  There  are  economists  who  would  argue  that  the 
automobile  has  paid  for  itself  by  its  usefulness,  but 
the  fact  still  exists  that  a  great  amount  of  labor  has 
been  diverted  from  producing  food,  clothing,  and  fuel 
to  the  production  of  “pleasure”  automobiles.  And 
this  is  the  case  with  many  other  conveniences  and  lux¬ 
uries.  It  is  admitted  that  mankind  deserves  these  re¬ 
finements  of  modern  civilization,  but  he  must  expect 
the  cost  of  living  to  increase  unless  counteracting 
measures  are  taken. 

The  economics  of  the  increasing  cost  of  living  and 
the  analysis  of  the  relations  of  necessities,  conven¬ 
iences,  and  luxuries  are  too  complex  to  be  thoroughly 

238 


THE  COST  OF  LIVING 


239 


discussed  here.  In  fact,  the  most  expert  economists 
would  disagree  on  many  points.  However,  it  is  cer¬ 
tain  that  the  cost  of  living  has  steadily  increased  dur¬ 
ing  the  past  century  and  it  is  reasonably  certain  that 
the  standards  of  the  present  civilization  are  responsi¬ 
ble  for  some  if  not  all  of  the  increase.  Increased  pro¬ 
duction  is  an  anchor  to  the  windward.  It  may  drag 
and  give  way  to  some  extent,  but  it  will  always  oppose 
the  course  of  the  cost  of  living. 

When  the  first  industrial  plant  was  lighted  by  gas, 
early  in  the  nineteenth  century,  the  aim  was  merely 
to  reinforce  daylight  toward  the  end  of  the  day.  Con¬ 
tinuous  operation  of  industrial  plants  was  not  prac¬ 
tised  in  those  days,  excepting  in  a  very  few  cases  where 
it  was  essential.  To-day  some  industries  operate  con¬ 
tinuously,  but  most  of  them  do  not.  In  the  latter  case 
the  consumer  pays  more  for  the  product  because  the 
percentage  of  fixed  or  overhead  charge  is  greater. 
Investment  in  ground,  buildings,  and  equipment  ex¬ 
acts  its  toll  continuously  and  it  is  obvious  that  three 
successive  shifts  producing  three  times  as  much  as 
a  single  day  shift,  or  as  much  as  a  trebled  day  shift, 
will  produce  the  less  costly  product.  In  the  former 
case  the  fixed  charge  is  distributed  over  the  produc¬ 
tion  of  continuous  operation,  but  in  the  latter  case 
the  production  of  a  single  day  shift  assumes  the  en¬ 
tire  burden.  Of  course,  there  are  many  factors  which 
enter  into  such  a  consideration  and  an  important  one 
is  the  desirability  of  working  at  night.  It  is  not  the 
intention  to  touch  upon  the  psychological  and  sociologi¬ 
cal  aspects  but  merely  to  look  coldly  upon  the  facts  per¬ 
taining  to  artificial  light  and  production. 


240 


ARTIFICIAL  LIGHT 


In  the  first  place,  it  has  been  proved  that  in  fac¬ 
tories  proper  lighting  as  obtained  by  artificial  means 
is  generally  more  satisfactory  than  the  natural  light¬ 
ing.  Of  course,  a  narrow  building  with  windows  on 
two  sides  or  a  one-story  building  with  a  saw-tooth 
roof  of  best  design  may  be  adequately  illuminated  by 
natural  light,  but  these  buildings  are  the  exception 
and  they  will  grow  rarer  as  industrial  districts  become 
more  congested.  Artificial  light  may  be  controlled  so 
that  light  of  a  satisfactory  quality  is  properly  di¬ 
rected  and  diffused.  Sufficient  intensities  of  illumina¬ 
tion  may  be  obtained  and  the  failure  of  artificial  light 
is  a  remote  possibility  as  compared  with  the  daily  fail¬ 
ure  of  natural  light.  With  increasing  cost  of  ground 
space,  factories  are  built  of  several  stories  and  with 
less  space  given  to  light  courts,  with  the  result  that  the 
ratio  of  window  area  to  that  of  the  floor  is  reduced. 
These  tendencies  militate  against  satisfactory  day¬ 
lighting.  In  the  smoky  congested  industrial  districts 
the  period  of  effective  daylight  is  gradually  diminish¬ 
ing  and  artificial  lighting  is  always  essential  at  least  as 
a  reinforcement  for  daylight.  It  has  been  proved  that 
proper  artificial  lighting — and  there  is  no  excuse  for 
improper  artificial  lighting — is  superior  to  most  in¬ 
terior  daylighting  conditions. 

Although  it  is  difficult  to  present  figures  in  a  brief 
discussion  of  this  character,  it  may  be  stated  that,  in 
general,  the  cost  of  adequate  artificial  light  is  about 
2  per  cent,  of  the  pay-roll  of  the  workers;  about  10 
per  cent,  of  the  rental  charges ;  and  only  a  fraction  of 
1  per  cent,  of  the  cost  of  the  manufactured  products. 
These  figures  vary  considerably,  but  they  represent 


LOCOMOTIVE  ELECTRIC  HEADLIGHT 


SEARCH-LIGHT  ON  A  FIRE-BOAT 


BUILDING  SHIPS  UNDER  ARTIFICIAL  LIGHT  AT  HOG  ISLAND  SHIPYARD 


THE  COST  OF  LIVING 


241 


conservative  average  estimates.  From  these  it  is  seen 
that  artificial  lighting  is  a  small  factor  in  adding  to  the 
cost  of  the  product.  But  does  artificial  lighting  add 
to  the  cost  of  a  product?  Many  examples  could  be 
cited  to  prove  that  proper  artificial  lighting  may  be 
responsible  for  an  actual  reduction  in  the  cost  of  the 
product. 

In  a  certain  plant  it  was  determined  that  the  work¬ 
men  each  lost  an  appreciable  part  of  an  hour  per  day 
because  of  inadequate  lighting.  A  properly  designed 
and  maintained  lighting-system  was  installed  and  the 
saving  in  the  wages  previously  lost,  more  than  cov¬ 
ered  the  operating-expense  of  the  artificial  lighting. 
Besides  really  costing  the  manufacturer  less  than  noth¬ 
ing,  the  new  artificial  lighting  system  was  responsible 
for  better  products,  decreased  spoilage,  minimized  ac¬ 
cidents,  and  generally  elevated  spirits  of  the  work¬ 
men.  In  some  cases  it  is  only  necessary  to  save  one 
minute  per  hour  per  workman  to  offset  entirely  the 
cost  of  lighting.  The  foregoing  and  many  other  ex¬ 
amples  illustrate  the  insignificance  of  the  cost  of 
lighting. 

The  effectiveness  of  artificial  lighting  in  reducing 
the  cost  of  living  is  easily  demonstrated  by  comparing 
the  output  of  a  factory  operating  on  one  and  two 
shifts  per  day  respectively.  In  a  well-lighted  factory 
which  operated  day  and  night  shifts,  the  cost  of  ade¬ 
quate  lighting  was  7  cents  per  square  foot  per  year. 
If  this  factory,  operating  only  in  the  daytime,  were 
to  maintain  the  same  output,  it  would  be  necessary  to 
double  its  size.  In  order  to  show  the  economic  value 
of  artificial  lighting  it  is  only  necessary  to  compare  the 


242 


ARTIFICIAL  LIGHT 


cost  of  lighting  with  the  rental  charge  of  the  addition 
and  of  its  equipment.  A  fair  rental  value  for  plant 
and  equipment  is  50  cents  per  square  foot  per  year; 
but  of  course  this  varies  considerably,  depending  upon 
the  type  of  plant  and  the  character  of  the  equipment. 
An  investigation  showed  that  this  value  varies  usually 
between  30  to  70  cents  per  square  foot  per  year.  Us¬ 
ing  the  mean  value,  50  cents,  it  is  seen  that  the  rental 
charge  is  about  seven  times  the  cost  of  lighting.  Fur¬ 
thermore,  there  is  a  saving  of  43  cents  per  square  foot 
per  year  during  the  night  operation  by  operating  the 
night  shift.  Of  course,  this  is  not  strictly  true  because 
a  depreciation  of  machinery  during  the  night  shift 
should  be  allowed  for.  These  fixed  charges  would  av¬ 
erage  slightly  more  than  half  as  much  in  the  case  of 
the  two-shift  factory  as  in  the  case  of  the  same  out¬ 
put  from  a  factory  twice  as  large  but  operating  only 
a  day  shift.  Incidentally,  the  two-shift  factory  need 
not  be  a  hardship  for  the  workers,  for,  if  the  eight- 
hour  shifts  are  properly  arranged,  the  worker  on  the 
night  shift  may  be  in  bed  by  midnight  and  the  ob¬ 
jection  to  a  disturbance  of  ordinary  hours  of  sleep  is 
virtually  eliminated. 

In  a  discussion  of  light  and  safety  presented  in  an¬ 
other  chapter  the  startling  industrial  losses  due  to  ac¬ 
cidents  are  shown  to  be  due  partially  to  inadequate  or 
improper  lighting.  About  one  fourth  of  the  total  num¬ 
ber  of  accidents  may  be  charged  to  defective  lighting. 
The  consumer  bears  the  burden  of  the  support  of  an 
unproducing  army  of  idle  men.  According  to  some 
experts  an  average  of  about  150,000  men  are  contin- 


THE  COST  OF  LIVING  243 

uously  idle  in  this  country  owing  to  inadequate  and 
improper  lighting. 

This  is  an  appreciable  factor  in  the  cost  of  living, 
but  the  greatest  effectiveness  of  artificial  lighting  in 
curtailing  costs  is  to  be  found  in  reducing  the  fixed 
charges  borne  by  the  product  through  the  operation 
of  two  shifts  and  by  directly  increasing  production 
owing  to  improved  lighting.  The  standard  of  arti¬ 
ficial-lighting  intensity  possessed  by  the  average  per¬ 
son  at  the  present  time  is  an  inheritance  from  the  past. 
In  those  days  when  artificial  light  was  much  more 
costly  than  at  present  the  tendency  naturally  was  to 
use  just  as  little  light  as  necessary.  That  attitude 
could  not  have  been  severely  criticized  in  those  early 
days  of  artificial  lighting,  but  it  is  inexcusable  to-day. 
Eyesight  and  greater  safety  from  accidents  are  in 
themselves  valuable  enough  to  warrant  adequate  light¬ 
ing,  but  besides  these  there  is  the  appeal  of  increased 
production. 

Outdoors  on  a  clear  summer  day  at  noon  the  intensity 
of  daylight  illumination  at  the  earth’s  surface  is  about 
10,000  foot-candles ;  in  other  words,  it  is  equal  to  the 
illumination  on  a  surface  produced  by  a  light-source 
equivalent  to  10,000  candles  at  a  distance  of  one  foot 
from  the  surface.  This  will  be  recognized  as  an  enor¬ 
mous  intensity  of  illumination.  On  a  cloudy  day  the 
intensity  of  illumination  at  the  earth’s  surface  may 
be  as  high  as  3000  foot-candles  and  on  a  “gloomy”  day 
the  illumination  at  the  earth’s  surface  may  be  1000 
foot-candles.  When  it  is  considered  that  mankind 
works  under  artificial  light  with  an  intensity  of  only 


244 


ARTIFICIAL  LIGHT 


a  few  foot-candles,  the  marvels  of  the  visual  apparatus 
are  apparent.  But  it  should  be  noted  that  the  eyes  of 
the  human  race  evolved  under  natural  light.  They 
have  been  used  to  great  intensities  when  called  upon 
for  their  greatest  efforts.  The  human  being  is  won¬ 
derfully  adaptive,  but  it  could  scarcely  be  hoped  that 
the  eyes  could  readjust  themselves  in  a  few  generations 
to  the  changed  conditions  of  low-intensity  artificial 
lighting.  There  is  no  complaint  against  the  range  of 
intensities  to  which  the  eye  responds,  for  in  range  of 
sensibility  it  is  superior  to  any  man-made  device. 

For  extremely  low  .brightnesses  another  set  of 
physiological  processes  come  into  play.  Based  purely 
upon  the  physiological  laws  of  vision  it  seems  reason¬ 
able  to  conclude  that  mankind  should  not  work  under 
artificial  illumination  as  low  as  has  been  considered 
necessary  owing  to  the  cost  in  the  past.  With  this 
principle  of  vision  as  a  foundation,  experiments  have 
been  made  with  greater  intensities  of  illumination  in 
the  industries  and  elsewhere  and  increased  production 
has  been  the  result.  In  a  test  in  a  factory  where  an 
adequate  record  of  production  was  in  effect  it  was 
found  that  an  increase  in  the  intensity  of  illumination 
from  4  to  12  foot-candles  increased  the  production  in 
various  operations.  The  lowest  increase  in  produc¬ 
tion  was  8  per  cent.,  the  highest  was  27  per  cent.,  and 
the  average  was  15  per  cent.  The  original  lighting 
in  this  case  was  better  than  that  of  the  typical  indus¬ 
trial  conditions,  so  that  it  seems  reasonable  to  expect 
a  greater  increase  in  production  when  a  change  is  made 
from  the  average  inadequate  lighting  of  a  factory  to  a 


THE  COST  OF  LIVING  245 

well-designed  lighting-system  giving  a  high  intensity 
of  illumination. 

In  another  test  the  production  under  a  poor  system 
of  lighting  by  means  of  bare  lamps  on  drop-cords  was 
compared  with  that  of  an  excellent  system  in  which 
well-designed  reflectors  were  used.  The  intensity  of 
illumination  in  the  latter  case  was  twenty-five  times 
that  of  the  former  and  the  production  was  increased 
in  various  operations  from  30  per  cent,  for  the  least 
increase  to  100  per  cent,  for  the  greatest  increase.  In¬ 
asmuch  as  the  energy  consumption  in  the  latter  case 
was  increased  seven  times  and  the  illumination  twenty- 
five  times,  it  is  seen  that  the  increase  in  intensity  of 
illumination  was  due  largely  to  the  use  of  proper  re¬ 
flectors  and  to  the  general  layout  of  the  new  lighting- 
system. 

In  another  case  a  10  per  cent,  increase  in  production 
was  obtained  by  increasing  the  intensity  of  illumina¬ 
tion  from  3  foot-candles  to  about  12  foot-candles. 
This  increase  of  four  times  in  the  intensity  of  illumina¬ 
tion  involved  an  increase  in  consumption  of  electrical 
energy  of  three  times  the  original  amount  at  an  in¬ 
crease  in  cost  equal  to  1.2  per  cent,  of  the  pay-roll.  In 
another  test  an  increase  of  10  per  cent,  in  production 
was  obtained  at  an  increase  in  cost  equal  to  less  than  1 
per  cent,  of  the  payroll.  The  efficiency  of  well-de¬ 
signed  lighting  installations  is  illustrated  in  this  case, 
for  the  illumination  intensity  was  increased  six  times 
by  doubling  the  consumption  of  electrical  energy. 

Various  other  tests  could  be  cited,  but  these  would 
merely  emphasize  the  same  results.  However,  it  may 


246 


ARTIFICIAL  LIGHT 


be  stated  that  the  factory  superintendents  involved  are 
convinced  that  adequate  and  proper  artificial  lighting 
is  a  great  factor  in  increasing  production.  Mr.  W.  A. 
Durgin,  who  conducted  the  tests,  has  stated  that  the 
average  result  of  increasing  the  intensity  of  illumina¬ 
tion  and  of  properly  designing  the  lighting  installa¬ 
tions  in  factories  will  be  at  least  a  15  per  cent,  in¬ 
crease  in  production  at  an  increased  cost  of  not  more 
than  5  per  cent,  of  the  pay-roll.  This  is  apparently 
a  conservative  statement.  When  it  is  considered  that 
generally  the  cost  of  lighting  is  only  a  fraction  of  1 
per  cent,  of  the  cost  of  products  to  the  consumer,  it  is 
seen  that  the  additional  cost  of  obtaining  an  increase 
of  15  per  cent,  in  production  is  inappreciable. 

Industrial  superintendents  are  just  beginning  to  see 
the  advantage  of  adequate  artificial  lighting,  but  the 
low  standards  of  lighting  which  were  inaugurated 
when  artificial  light  was  much  more  costly  than  it  is 
to-day  persist  tenaciously.  When  high  intensities  of 
proper  illumination  are  once  tried,  they  invariably 
prove  successful  in  the  industries.  Not  only  does  the 
worker  see  all  his  operations  better,  but  there  appears 
to  be  an  enlivening  effect  upon  individuals  under  the 
higher  intensities  of  illumination.  Mankind  chooses 
a  dimly  lighted  room  in  which  to  rest  and  to  dream. 
A  room  intensely  lighted  by  means  of  well-designed 
units  which  are  not  glaring  is  comfortable  but  not  con¬ 
ducive  to  quiet  contemplation.  It  is  a  place  in  which 
to  be  active.  This  is  perhaps  one  of  the  factors  which 
makes  for  increased  production  under  adequate  light¬ 
ing. 

Civilization  has  just  passed  the  threshold  of  the  age 


THE  COST  OF  LIVING 


247 


of  adequate  artificial  lighting  and  only  a  small  per¬ 
centage  of  the  industries  have  increased  their  lighting 
standards  commensurately  to  the  possibilities  of  the 
present  time.  If  high-intensity  artificial  lighting  was 
installed  in  all  the  industries  and  a  15  per  cent,  in¬ 
crease  in  production  resulted,  as  tests  appear  to  indi¬ 
cate,  the  increased  production  would  be  equal  to  that 
of  nearly  two  million  workers.  This  great  increase  in 
output  is  brought  about  by  lighting  at  an  insignificant 
increase  in  cost  but  without  the  additional  consump¬ 
tion  of  food  or  clothing.  Besides  this  increase  in  pro¬ 
duction  there  is  the  decrease  in  spoilage.  The  saving 
possible  in  this  respect  through  adequate  lighting  has 
been  estimated  for  the  industries  of  this  country  at 
$100,000,000.  If  mankind  is  to  have  conveniences  and 
luxuries,  efficienc}^  in  production  must  be  practised  to 
the  utmost  and  in  the  foregoing  a  proved  means  has 
been  discussed. 

There  are  many  other  ways  in  which  artificial  light 
may  serve  in  increasing  production.  Man  has  found 
that  eight  hours  of  sleep  is  sufficient  to  keep  him  fit 
for  work  if  he  has  a  sufficient  amount  of  recreation. 
Before  the  advent  of  artificial  light  the  activities  of  the 
primitive  savage  were  halted  by  darkness.  This  may 
have  been  Nature’s  intention,  but  civilized  man  has 
adapted  himself  to  the  changed  conditions  brought 
about  by  efficient  and  adequate  artificial  light.  There 
appears  to  be  no  fundamental  reason  for  not  imposing 
an  artificial  day  upon  plants,  animals,  chemical  proc¬ 
esses,  etc.;  and,  in  fact,  experiments  are  being  prose¬ 
cuted  in  these  directions. 

The  hen,  when  permitted  to  follow  her  natural 


248  . 


ARTIFICIAL  LIGHT 


course,  rises  with  the  sun  and  goes  to  roost  at  sunset. 
During  the  winter  months  she  puts  in  short  days  off 
the  roost.  It  has  been  shown  that  an  artificial  day, 
made  by  piecing  out  daylight  by  means  of  artificial 
light,  might  keep  the  hen  scratching  and  feeding  longer, 
with  an  increased  production  of  eggs  as  a  result. 
Many  experiments  of  this  character  have  been  carried 
out,  and  there  appears  to  be  a  general  conclusion  that 
the  use  of  artificial  light  for  this  purpose  is  profitable. 

Experiments  conducted  recently  by  the  agricultural 
department  of  a  large  university  indicate  that  in  poul¬ 
try  husbandry,  when  artificial  light  is  applied  to  the 
right  kind  of  stock  with  correct  methods  of  feeding, 
the  distribution  of  egg-production  throughout  the 
whole  year  can  be  radically  changed.  The  supply  of 
eggs  may  be  increased  in  autumn  and  winter  and  de¬ 
creased  in  spring  and  summer.  Data  on  the  amount 
of  illumination  have  not  been  published,  but  it  is  said 
that  the  most  satisfactory  results  have  been  obtained 
when  the  artificial  illumination  is  used  from  sunset 
until  about  9  p.  m.  throughout  the  year. 

An  increase  of  30  to  40  per  cent,  in  the  number  of 
eggs  laid  on  a  poultry-farm  in  England  as  the  result 
of  installing  electric  lamps  in  the  hen-houses  was  re¬ 
ported  in  1913.  On  this  farm  there  were  nearly  200 
yards  of  hen-houses  containing  about  6000  hens,  and 
the  runs  were  lighted  on  dark  mornings  and  early 
nights  of  the  year  preceding  the  report.  About  300 
small  lamps  varying  from  8  to  32  candle-power  were 
used  in  the  houses.  It  was  found  that  an  imitation  of 
sunset  was  necessary  by  switching  off  the  32  candle- 
power  lamps  at  6  p.  m.  and  the  16  candle-power  lamps 


THE  COST  OF  LIVING 


249 


at  9 : 30.  This  left  only  the  8  candle-power  lamps 
burning,  and  in  the  faint  illumination  the  hens  sought 
the  roosting-places.  At  10  p.  m.  the  remaining  lights 
were  extinguished.  It  was  found  that  if  all  the  lights 
were  extinguished  suddenly  the  fowls  went  to  sleep  on 
the  ground  and  thus  became  a  prey  to  parasites.  The 
increase  in  production  of  eggs  is  brought  about  merely 
by  keeping  the  fowls  awake  longer.  On  the  same  farm 
the  growth  of  chicks  incubated  during  the  winter 
months  increased  by  one  third  through  the  use  of  elec¬ 
tric  light  which  kept  them  feeding  longer. 

Many  fishermen  will  testify  that  artificial  light  seems 
to  attract  fish,  and  various  reports  have  been  circu¬ 
lated  regarding  the  efficacy  of  using  artificial  light  for 
this  purpose  on  a  commercial  scale.  One  report  which 
bears  the  earmarks  of  authenticity  is  from  Italy,  where 
it  is  said  that  electric  lights  were  successfully  used  as 
“bait”  to  augment  the  supply  of  fish  during  the  war. 
The  lamps  were  submerged  to  a  considerable  depth 
and  the  fish  were  attracted  in  such  large  numbers  that 
the  use  of  artificial  light  was  profitable.  The  claims 
made  were  that  the  supply  of  fish  was  not  only  in¬ 
creased  by  night  fishing  but  that  a  number  of  fishermen 
were  thereby  released  for  national  service  during  the 
war.  An  interesting  incident  pertaining  to  fish,  but 
perhaps  not  an  important  factor  in  production,  is  the 
use  of  electric  lights  in  the  summer  over  the  reser¬ 
voirs  of  a  fish  hatchery.  These  lights,  which  hang  low, 
attract  myriads  of  bugs,  many  of  which  fall  in  the  wa¬ 
ter  and  furnish  natural  and  inexpensive  food  for  the 
fish. 

Many  experiments  have  been  carried  out  in  the  fore- 


250  , 


ARTIFICIAL  LIGHT 


ing  of  plants  by  means  of  artificial  light.  Some  of 
these  were  conducted  forty  years  ago,  when  artificial 
light  was  more  costly  than  at  the  present  time.  Of 
course,  it  is  well  known  that  light  is  essential  to  plant 
life  and  in  general  it  is  reasonable  to  believe  that  day¬ 
light  is  the  most  desirable  quality  of  light  for  plants. 
In  greenhouses  the  forcing  of  plants  is  desirable,  ow¬ 
ing  to  the  restricted  area  for  cultivation.  It  has  been 
established  that  some  of  the  ultra-violet  rays  which  are 
absorbed  or  not  transmitted  by  glass  are  harmful  to 
growing  plants.  For  this  reason  an  arc-lamp  designed 
for  forcing  purposes  should  be  equipped  with  a  glass 
globe.  F.  W.  Rane  reported  in  1894  upon  some  ex¬ 
periments  with  electric  carbon-filament  lamps  in  green¬ 
houses  in  which  satisfactory  results  were  obtained  by 
using  the  artificial  light  several  hours  each  night. 
Prof.  L.  H.  Bailey  also  conducted  experiments  with  the 
arc-lamp  and  concluded  that  there  were  beneficial  re¬ 
sults  if  the  light  was  filtered  through  clear  glass. 
Without  considering  the  details  of  the  experiment,  we 
find  some  of  Rane’s  conclusions  of  interest,  especially 
when  it  is  remembered  that  the  carbon-filament  lamps 
used  at  that  time  were  of  very  low  efficiency  compared 
with  the  filament  lamps  at  the  present  time.  Some  of 
his  conclusions  were  as  follows : 

The  incandescent  electric  light  has  a  marked  effect 
upon  greenhouse  plants. 

The  light  appears  to  be  beneficial  to  some  plants 
grown  for  foliage,  such  as  lettuce.  The  lettuce  was 
earlier,  weighed  more  and  stood  more  erect. 

Flowering  plants  blossomed  earlier  and  continued  to 
bloom  longer  under  the  light. 


THE  COST  OF  LIVING 


251 


The  light  influences  some  plants,  such  as  spinach  and 
endive,  to  quickly  run  to  seed,  which  is  objectionable  in 
forcing  these  plants  for  sale. 

The  stronger  the  candle-power  the  more  marked  the 
results,  other  conditions  being  the  same. 

Most  plants  tended  toward  a  taller  growth  under 
the  light. 

It  is  doubtful  whether  the  incandescent  light  can  be 
used  in  the  greenhouse  from  a  practical  and  economic 
standpoint  on  other  plants  than  lettuce  and  perhaps 
flowering  plants;  and  at  present  prices  (1894)  it  is  a 
question  if  it  will  pay  to  employ  it  even  for  these. 

There  are  many  points  about  the  incandescent  elec¬ 
tric  light  that  appear  to  make  it  preferable  to  the  arc 
light  for  greenhouse  use. 

Although  we  have  not  yet  thoroughly  established  the 
economy  and  practicability  of  the  electric  light  upon 
plant  growth,  still  I  am  convinced  that  there  is  a  fu¬ 
ture  in  it. 

These  are  encouraging  conclusions,  considering  the 
fact  that  the  cost  of  light  from  incandescent  lamps  at 
the  present  time  is  only  a  small  fraction  of  its  cost  at 
that  time. 

In  an  experiment  conducted  in  England  in  1913  mer¬ 
cury  glass-tube  arcs  were  used  in  one  part  of  a  hot¬ 
house  and  the  other  part  was  reserved  for  a  control 
test.  The  same  kind  of  seeds  were  planted  in  the  two 
parts  of  the  hothouse  and  all  conditions  were  main¬ 
tained  the  same,  excepting  that  a  mercury-vapor  lamp 
was  operated  a  few  hours  in  the  evening  in  one  of  them. 
Miss  Dudgeon,  who  conducted  the  test,  was  enthusi¬ 
astic  over  the  results  obtained.  Ordinary  vegetable 
seeds  and  grains  germinated  in  eight  to  thirteen  days 
in  the  hothouse  in  which  the  artificial  light  was  used 


252 


ARTIFICIAL  LIGHT 


to  lengthen  the  day.  In  the  other,  germination  took 
place  in  from  twelve  to  fifty-seven  days.  In  all  cases 
at  least  several  days  were  saved  in  germination  and  in 
some  cases  several  weeks.  Flowers  also  increased  in 
foliage,  and  a  25  per  cent,  increase  in  the  crop  of  straw¬ 
berries  was  noted.  Seedlings  produced  under  the  forc¬ 
ing  by  artificial  light  needed  virtually  no  hardening  be¬ 
fore  being  planted  in  the  open.  Professor  Priestley 
of  Bristol  University  said  of  this  work : 

The  light  seems  to  have  been  extraordinarily  effica¬ 
cious,  producing  accelerated  germination,  increased 
growth,  greater  depth  of  color,  and  more  important 
still,  no  signs  of  lanky,  unnatural  extension  of  plant 
usually  associated  with  forcing.  Rather  the  plants 
exposed  to  the  radiation  seem  to  have  grown  if  any¬ 
thing  more  sturdy  than  the  control  plants.  A  struc¬ 
tural  examination  of  the  experimental  and  control 
plants  carried  out  by  means  of  the  microscope  fully 
confirmed  Miss  Dudgeon’s  statements  both  as  to  depth 
of  color  and  greater  sturdiness  of  the  treated  plants. 

Unfortunately  there  is  much  confusion  amid  the  re¬ 
sults  of  experiments  pertaining  to  the  effects  of  differ¬ 
ent  rays,  including  ultra-violet,  visible  and  infra-red, 
upon  plant  growth.  If  this  aspect  was  thoroughly  es¬ 
tablished,  investigations  could  be  outlined  to  greater 
advantage  and  efficient  light-sources  could  be  chosen 
with  certainty.  There  is  the  discouraging  feature  that 
the  average  intensity  of  daylight  illumination  from 
sunrise  to  sunset  in  the  summer-time  is  several  thou¬ 
sand  foot-candles.  The  cost  of  obtaining  this  great 
intensity  by  means  of  artificial  light  would  be  prohibi¬ 
tive.  However,  the  daylight  illumination  in  a  green- 


THE  COST  OF  LIVING 


253 


house  in  winter  is  very  much  less  than  the  intensity 
outdoors  in  summer.  Indeed,  this  intensity  perhaps 
averages  only  a  few  hundred  foot-candles  in  winter. 
There  is  encouragement  in  this  fact  and  there  is  hope 
that  a  little  light  is  relatively  much  more  effective 
than  a  great  amount.  Expressed  in  another  manner, 
it  is  possible  that  a  little  light  is  much  more  effective 
than  no  light  at  all.  Experiments  with  artificial  light 
indicate  very  generally  an  increased  growth. 

Recently  Hayden  and  Steinmetz  experimented  with 
a  plot  of  ground  5  feet  by  9  feet,  over  which  were  hung 
five  500-watt  gas-filled  tungsten  lamps  3  feet  above  the 
ground  and  17  inches  apart.  The  lamps  were  equipped 
with  reflectors  and  the  resulting  illumination  was  700 
foot-candles.  This  is  an  extremely  high  intensity  of 
artificial  illumination  and  is  comparable  with  daylight 
in  greenhouses.  The  only  seeds  planted  were  those 
of  string  beans  and  two  beds  were  carried  through 
to  maturity,  one  lighted  by  daylight  only  and  the  other 
by  daylight  and  artificial  light,  the  latter  being  in  op¬ 
eration  twenty-fours  hours  per  day.  The  plants  under 
the  additional  artificial  light  grew  more  rapidly  than 
the  others,  and  of  the  various  records  kept  the  gain 
in  time  was  in  all  cases  about  50  per  cent.  From  the 
standpoint  of  profitableness  the  artificial  lighting  was 
not  justified.  However,  there  are  several  points  to 
be  brought  out  before  considering  this  conclusion  too 
seriously.  First,  it  appears  unwise  to  use  the  artificial 
light  during  the  day;  second,  it  appears  possible  that 
a  few  hours  of  artificial  light  in  the  evening  would 
suffice  for  considerable  forcing;  third,  it  is  possible  that 
a  much  lower  intensity  of  artificial  light  might  be  more 


254 


ARTIFICIAL  LIGHT 


effective  per  lumen  than  the  great  intensity  used; 
fourth,  it  is  quite  possible  that  some  other  efficient 
light-source  may  be  more  effective  in  forcing  the 
growth  of  plants.  These  and  many  other  factors  must 
be  carefully  determined  before  judgment  can  be  passed 
on  the  efficacy  of  artificial  light  in  reducing  the  cost  of 
living  in  this  direction.  Certainly,  artificial  light  has 
been  shown  to  increase  the  growth  of  plants  and  it 
appears  probable  that  future  generations  at  least  will 
find  it  profitable  to  use  the  efficient  light-producers  of 
the  coming  ages  in  this  manner. 

Many  other  instances  could  be  cited  in  which  arti¬ 
ficial  light  is  very  closely  associated  with  the  cost  of 
living.  Overseas  shipment  of  fruit  from  the  Canadian 
Northwest  is  responsible  for  a  decided  innovation  in 
fruit-picking.  In  searching  for  a  cause  of  rotting  dur¬ 
ing  shipment  it  was  finally  concluded  that  the  tempera¬ 
ture  at  the  time  of  picking  was  the  controlling  factor. 
As  a  consequence,  daytime  was  considered  undesirable 
for  picking  and  an  electric  company  supplied  electric 
lighting  for  the  orchards  in  order  that  the  picking 
might  be  done  during  the  cool  of  night.  This  change 
is  said  to  have  remedied  the  situation.  Cases  of 
threshing  and  other  agricultural  operations  being  car¬ 
ried  on  at  night  are  becoming  more  numerous.  These 
are  just  the  beginnings  of  artificial  light  in  a  new  field 
or  in  a  new  relation  to  civilization.  Its  economic  value 
has  been  demonstrated  in  the  ordinary  fields  of  light¬ 
ing  and  these  new  applications  are  merely  the  initial 
skirmishes  which  precede  the  conquest  of  new  terri¬ 
tory.  The  modern  illuminants  have  been  developed 


THE  COST  OF  LIVING 


255 


so  recently  that  the  new  possibilities  have  not  yet  been 
established.  However,  artificial  light  is  already  a  fac¬ 
tor  on  the  side  of  the  people  in  the  struggle  against 
the  increasing  cost  of  living,  and  its  future  in  this  di¬ 
rection  is  still  more  promising. 


XIX 

ARTIFICIAL  LIGHT  AND  CHEMISTRY 


Some  one  in  an  early  century  was  the  first  to  notice 
that  the  sun’s  rays  tanned  the  skin,  and  this  unknown 
individual  made  the  initial  discovery  in  what  is  now 
an  extensive  branch  of  science  known  as  photo-chem¬ 
istry.  The  fading  of  dyes,  the  bleaching  of  textiles, 
the  darkening  of  silver  salts,  the  synthesis  and  decom¬ 
position  of  compounds  are  common  examples  of  chem¬ 
ical  reactions  induced  by  light.  There  are  thousands 
of  other  examples  of  the  chemical  effects  of  light  some 
of  which  have  been  utilized  by  mankind.  Others  await 
the  development  of  more  efficient  light-sources  emitting 
greater  quantities  of  active  rays,  and  many  still  re¬ 
main  interesting  scientific  facts  without  any  apparent 
practical  applications  at  the  present  time.  Visible  and 
ultra-violet  rays  are  the  radiations  almost  entirely  re¬ 
sponsible  for  photochemical  reactions,  but  the  most 
active  of  these  are  the  blue,  violet,  and  ultra-violet 
rays.  These  are  often  designated  chemical  or  actinic 
rays  in  order  to  distinguish  the  group  as  a  whole  from 
other  groups  such  as  ultra-violet,  visible,  and  infra¬ 
red.  Light  is  a  unique  agent  in  chemical  reactions 
because  it  is  not  a  material  substance.  It  neither  con¬ 
taminates  nor  leaves  a  residue.  Although  much  in¬ 
formation  pertaining  to  photochemistry  has  been  avail¬ 
able  for  years,  the  absence  of  powerful  light-sources 

256 


ARTIFICIAL  LIGHT  IN  PHOTOGRAPHY 


Swimming  pool 


City  waterworks 


STERILIZING  WATER  WITH  RADIANT  ENERGY  FROM  QUARTZ  MERCURY-ARCS 


ARTIFICIAL  LIGHT  AND  CHEMISTRY  257 


emitting  so-called  chemical  rays  in  large  quantities  in¬ 
hibited  the  practical  development  of  the  science  of 
photochemistry.  Even  to-day,  with  vast  applications 
of  light  in  this  manner,  mankind  is  only  beginning  to 
utilize  its  chemical  powers. 

Although  it  appears  that  the  chemical  action  of  light 
was  known  to  the  ancients,  the  earliest  photochemical 
investigations  which  could  be  considered  scientific  and 
systematic  were  those  of  K.  W.  Scheele  in  1777  on 
silver  salts.  An  extract  from  his  own  account  is  as 
follows : 

I  precipitated  a  solution  of  silver  by  sal-ammoniac ; 
then  I  edulcorated  (washed)  it  and  dried  the  precipi¬ 
tate  and  exposed  it  to  the  beams  of  the  sun  for  two 
weeks;  after  which  I  stirred  the  powder  and  repeated 
the  same  several  times.  Hereupon  I  poured  some 
caustic  spirit  of  sal-ammoniac  (strong  ammonia)  on 
this,  in  all  appearance,  black  powder,  and  set  it  by  for 
digestion.  This  menstruum  (solvent)  dissolved  a 
quantity  of  luna  cornua  (horn  silver),  though  some 
black  powder  remained  undissolved.  The  powder  hav¬ 
ing  been  washed  was,  for  the  greater  part,  dissolved 
by  a  pure  acid  of  nitre  (nitric  acid),  which,  by  the  op¬ 
eration,  acquired  volatility.  This  solution  I  precipi¬ 
tated  again  by  means  of  sal-ammoniac  into  horn  sil¬ 
ver.  Hence  it  follows  that  the  blackness  which  the 
luna  cornua  acquires  from  the  sun’s  light,  and  like¬ 
wise  the  solution  of  silver  poured  on  chalk,  is  silver  by 
reduction.  I  mixed  so  much  of  distilled  water  with  the 
well-washed  horn  silver  as  would  just  cover  this  pow¬ 
der.  The  half  of  this  mixture  I  poured  into  a  white 
crystal  phial,  exposed  it  to  the  beams  of  the  sun,  and 
shook  it  several  times  each  day;  the  other  half  I  set 
in  a  dark  place.  After  having  exposed  the  one  mix¬ 
ture  during  the  space  of  two  weeks,  I  filtrated  the  wa- 


258  , 


ARTIFICIAL  LIGHT 


ter  standing*  over  the  horn  silver,  grown  already  black ; 
I  let  some  of  this  water  fall  by  drops  in  a  solution 
of  silver,  which  was  immediately  precipitated  into 
horn  silver. 

This  extract  shows  that  Scheele  dealt  with  the  reduc¬ 
ing  action  of  light.  He  found  that  silver  chloride  was 
decomposed  by  light  and  that  there  was  a  liberation 
of  chlorine.  However,  it  was  learned  later  that  dried 
silver  chloride  sealed  in  a  tube  from  which  the  air  was 
exhausted  is  not  discolored  by  light  and  that  sub¬ 
stances  must  be  present  to  absorb  the  chlorine. 
Scheele ’s  work  aroused  much  interest  in  photochemi¬ 
cal  effects  and  many  investigations  followed.  In  many 
of  these  the  superiority  of  blue,  violet,  and  ultra-violet 
rays  was  demonstrated.  In  1802  the  first  photograph 
was  made  by  Wedgwood,  who  copied  paintings  upon 
glass  and  made  profiles  by  casting  shadows  upon  a 
sensitive  chemical  compound.  However,  he  was  not 
able  to  fix  the  image.  Much  study  and  experimenta¬ 
tion  were  expended  upon  photochemical  effects,  espe¬ 
cially  with  silver  compounds,  before  Niepce  developed 
a  method  of  producing  pictures  which  were  subse¬ 
quently  unaffected  by  light.  Later  Daguerre  became 
associated  with  Niepce  and  the  famous  daguerreotype 
was  the  result.  Apparently  the  latter  was  chiefly  re¬ 
sponsible  for  the  development  of  this  first  commercial 
process,  the  products  of  which  are  still  to  be  found  in 
the  family  album.  A  century  has  elapsed  since  this 
earliest  period  of  commercial  photography,  and  dur¬ 
ing  each  year  progress  has  been  made,  until  at  the 
present  time  photography  is  thoroughly  woven  into  the 
activities  of  civilized  mankind. 


ARTIFICIAL  LIGHT  AND  CHEMISTRY  259 


In  those  earliest  years  a  person  was  obliged  to  sit 
motionless  in  the  sun  for  minutes  in  order  to  have  his 
picture  taken.  The  development  of  a  century  is  ex¬ 
emplified  in  the  “  snapshot’ ’  of  the  present  time.  Pho¬ 
tographic  exposures  outdoors  at  present  are  commonly 
one  thousandth  of  a  second,  and  indoors  under  modern 
artificial  light  miles  of  4  ‘  moving-picture  ’  ’  film  are 
made  daily  in  which  the  individual  exposures  are  very 
small  fractions  of  a  second.  Artificial  light  is  play¬ 
ing  a  great  part  in  this  branch  of  photochemistry,  and 
the  development  of  artificial  light  for  the  various  pho¬ 
tographic  needs  is  best  emphasized  by  reminding  the 
reader  that  the  sources  must  be  generally  comparable 
with  the  sun  in  actinic  or  chemical  power.  The  inten¬ 
sity  of  illumination  due  to  sunlight  on  a  clear  day  when 
the  sun  is  near  the  zenith  is  commonly  10,000  foot- 
candles  on  a  surface  perpendicular  to  the  direct  rays. 
This  is  equivalent  to  the  illumination  due  to  a  source 
of  90,000  candle-power  at  a  distance  of  three  feet.  The 
sun  delivers  about  200,000,000,000  horse-power  to  the 
earth  continuously,  which  is  estimated  to  be  about  one 
million  times  the  amount  of  power  generated  artifi¬ 
cially  on  the  earth.  Of  this  inconceivable  quantity  of 
energy  a  small  part  is  absorbed  by  vegetation,  some  is 
reflected  and  radiated  back  into  space,  and  the  balance 
heats  the  earth.  To  store  some  of  this  energy  so  that 
it  may  be  utilized  at  will  in  any  desired  form  is  one 
of  the  dreams  of  science.  However,  artificial  light- 
sources  are  depended  upon  at  present  in  many  photo¬ 
graphic  and  other  chemical  processes. 

Although  two  illuminants  may  be  of  the  same  lum¬ 
inous  intensity,  they  may  differ  widely  in  actinic  value. 


260  , 


ARTIFICIAL  LIGHT 


It  is  impossible  to  rate  the  different  illuminants  in  a 
general  manner  as  to  actinic  value  because  the  various 
photochemical  reactions  are  not  affected  to  the  same 
extent  by  rays  of  a  given  wave-length.  Nearly  all  hu¬ 
man  eyes  see  visible  rays  in  approximately  the  same 
manner,  but  the  multitude  of  chemical  reactions  show 
a  wide  variation  in  sensitivity  to  the  various  rays. 
For  example,  one  photographic  emulsion  may  be  sen¬ 
sitive  only  to  ultra-violet,  violet,  and  blue  rays  and  an¬ 
other  to  all  these  rays  and  also  to  the  green,  yellow, 
and  red.  Therefore,  one  illuminant  may  be  superior 
to  another  for  one  photochemical  reaction,  while  the 
reverse  may  be  true  in  the  case  of  another  reaction. 
In  general,  it  may  be  said  that  the  arc-lamps  including 
the  mercury-arcs  provide  the  most  active  illuminants 
for  photochemical  processes ;  however,  a  large  number 
of  electric  incandescent  filament  lamps  are  used  in 
photographic  work. 

The  photo-engraver  has  been  independent  of  sun¬ 
light  since  the  practical  development  of  his  art.  In 
fact,  the  printer  could  not  depend  upon  sunlight  for 
making  the  engravings  which  are  used  to  illustrate  the 
magazines  and  newspapers.  The  newspaper  photog¬ 
rapher  may  make  a  1  ‘  flashlight ’  ’  exposure,  develop  his 
negative,  and  make  a  print  from  it  under  artificial 
light.  He  may  turn  this  over  to  the  photo-engraver 
who  carries  out  his  work  by  means  of  powerful  arc- 
lamps  and  in  an  hour  or  two  after  the  original  ex¬ 
posure  was  made  the  newspaper  containing  the  illus¬ 
tration  is  being  sold  on  the  streets. 

The  moving-picture  studio  is  independent  of  day¬ 
light  in  indoor  settings  and  there  is  a  tendency  toward 


ARTIFICIAL  LIGHT  AND  CHEMISTRY  261 


the  exclusive  use  of  artificial  light.  In  this  field  mer¬ 
cury-vapor  lamps,  arc-lamps,  and  tungsten  photo¬ 
graphic  lamps  are  used.  Similarly,  in  the  portrait 
studio  there  is  a  tendency  for  the  photographer  to 
leave  the  skylighted  upper  floors  and  to  utilize  arti¬ 
ficial  light.  In  this  field  the  tungsten  photographic 
lamp  is  gaining  in  popularity,  owing  to  its  simplicity 
and  to  other  advantages.  Artificial  light  in  general  is 
more  satisfactory  than  natural  light  for  many  kinds 
of  photographic  work  because  through  the  ease  of  con¬ 
trolling  it  a  greater  variety  of  more  artistic  effects 
may  be  obtained.  In  ordinary  photographic  printing 
tungsten  lamps  are  widely  used,  but  in  blue-printing 
the  white  flame-arc  and  the  mercury-vapor  lamp  are 
generally  employed.  Not  many  years  ago  the  blue- 
printer  waited  for  the  sun  to  appear  in  order  to  make 
his  prints,  but  to-day  large  machines  operate  continu¬ 
ously  under  the  light  of  powerful  artificial  sources. 
How  many  realize  that  the  blue-print  is  almost  uni¬ 
versally  at  the  foundation  of  everything  at  the  present 
time?  Not  only  are  products  made  from  blue-prints 
but  the  machinery  which  makes  the  products  is  built 
from  blue-prints.  Even  the  building  which  houses  the 
machinery  is  first  constructed  from  blue-prints.  They 
form  an  endless  chain  in  the  activities  of  present  civ¬ 
ilization. 

Artificial  light  has  been  a  great  factor  in  the  practi¬ 
cal  development  of  photography  and  it  is  looked  upon 
for  aid  in  many  other  directions.  Although  there  is 
a  multitude  of  reactions  in  photographic  processes 
which  are  brought  about  by  exposure  to  light,  these 
represent  relatively  few  of  the  photochemical  reac- 


262  , 


ARTIFICIAL  LIGHT 


tions.  In  general,  it  may  be  stated  that  light  is  cap¬ 
able  of  causing  nearly  every  type  of  reaction.  The 
chemical  compounds  which  are  photo-sensitive  are  very 
numerous.  Many  of  the  compounds  of  silver,  gold, 
platinum,  mercury,  iron,  copper,  manganese,  lead, 
nickel,  and  tin  are  photo-sensitive  and  these  have  been 
widely  investigated.  Light  and  oxygen  cause  many 
oxidation  reactions  and,  on  the  other  hand,  light  re¬ 
duces  many  compounds  such  as  silver  salts,  even  to 
the  extent  of  liberating  the  metal.  Oxygen  is  con¬ 
verted  partially  into  ozone  under  the  influence  of  cer¬ 
tain  rays  and  there  are  many  examples  of  polymeri¬ 
zation  caused  by  light. 

Various  allotropic  changes  of  the  elements  are  due 
to  the  influence  of  light;  for  example,  a  sulphur  solu¬ 
ble  in  carbon  disulphide  is  converted  into  sulphur  which 
is  insoluble,  and  the  rate  of  change  of  yellow  phos¬ 
phorus  into  the  red  variety  is  greatly  accelerated  by 
light.  Hydrogen  and  chlorine  combine  under  the  ac¬ 
tion  of  light  with  explosive  rapidity  to  form  hydro¬ 
chloric  acid  and  there  are  many  other  examples  of  the 
synthesizing  action  of  light.  Carbon  monoxide  and 
chlorine  combine  to  form  phosgene  and  the  combina¬ 
tion  of  chlorine,  bromine,  and  iodine,  with  organic 
compounds,  is  much  hastened  by  exposing  the  mixture 
to  light.  In  a  similar  manner  many  decompositions 
are  due  to  light;  for  example,  hydrogen  peroxide  is  de¬ 
composed  into  water  and  oxygen.  This  suggests  the 
reason  for  the  use  of  brown  bottles  as  containers  for 
many  chemical  compounds.  Such  glass  does  not  trans¬ 
mit  appreciably  the  so-called  actinic  or  chemical  rays. 

There  is  a  large  number  of  reactions  due  to  light  in 


ARTIFICIAL  LIGHT  AND  CHEMISTRY  263 


organic  chemistry  and  one  of  fundamental  importance 
to  mankind  is  the  effect  of  light  on  the  chlorophyll,  the 
green  coloring  matter  in  vegetation.  No  permanent 
change  takes  place  in  the  chlorophyll,  but  by  the  action 
of  light  it  enables  the  plant  to  absorb  oxygen,  carbon 
dioxide,  and  water  and  to  use  these  to  build  up  the  com¬ 
plex  organic  substances  which  are  found  in  plants. 
Radiant  energy  or  light  is  absorbed  and  converted 
into  chemical  energy.  This  use  of  radiant  energy  oc¬ 
curs  only  in  those  parts  of  the  plant  in  which  chloro¬ 
phyll  is  present,  that  is,  in  the  leaves  and  stems. 
These  parts  absorb  the  radiant  energy  and  take  carbon 
dioxide  from  the  air  through  breathing  openings. 
They  convert  the  radiant  energy  into  chemical  energy 
and  use  this  energy  in  decomposing  the  carbon  dioxide. 
The  oxygen  is  exhausted  and  the  carbon  enters  into 
the  structure  of  the  plant.  The  energy  of  plant  life 
thus  comes  from  radiant  energy  and  with  this  aid  the 
simple  compounds,  such  as  the  carbon  dioxide  of  the 
air  and  the  phosphates  and  nitrates  of  the  soil,  are 
built  into  complex  structures.  Thus  plants  are  con¬ 
structive  and  synthetic  in  operation.  It  is  interesting 
to  note  that  the  animal  organism  converts  complex 
compounds  into  mechanical  and  heat  energy.  The  ani¬ 
mal  organism  depends  upon  the  synthetic  work  of 
plants,  consuming  as  food  the  complex  structures  built 
by  them  under  the  action  of  light.  For  example,  plants 
inhale  carbon  dioxide,  liberate  the  oxygen,  and  store 
the  carbon  in  complex  compounds,  while  the  animal 
uses  oxygen  to  bum  up  the  complex  compounds  de¬ 
rived  from  plants  and  exhales  carbon  dioxide.  It  is  a 
beautiful  cycle,  which  shows  that  ultimately  all  life  on 


264 


ABTIFICIAL  LIGHT 


earth  depends  upon  light  and  other  radiant  energy  as¬ 
sociated  with  it.  Contrary  to  most  photochemical  re¬ 
actions,  it  appears  that  plant  life  utilize  yellow,  red, 
and  infra-red  energy  more  than  the  blue,  violet,  and 
ultra-violet. 

In  general,  great  intensities  of  blue  light  and  of  the 
closely  associated  rays  are  necessary  for  most  photo¬ 
chemical  reactions  with  which  man  is  industrially  inter¬ 
ested.  It  has  been  found  that  the  white  flame-arc  ex¬ 
cels  other  artificial  light-sources  in  hastening  the 
chlorination  of  natural  gas  in  the  production  of  chloro¬ 
form.  One  advantage  of  the  radiation  from  this  light- 
source  is  that  it  does  not  extend  far  into  the  ultra¬ 
violet,  for  the  ultra-violet  rays  of  short  wave-lengths 
decompose  some  compounds.  In  other  words,  it  is  nec¬ 
essary  to  choose  radiation  which  is  effective  but  which 
does  not  have  rays  associated  with  it  that  destroy  the 
desired  products  of  the  reaction.  By  the  use  of  a  shunt 
across  the  arc  the  light  can  be  gradually  varied  over  a 
considerable  range  of  intensity.  Another  advantage  of 
the  flame-arc  in  photochemistry  is  the  ease  with  which 
the  quality  or  spectral  character  of  the  radiant  energy 
may  be  altered  by  varying  the  chemical  salts  used  in 
the  carbons.  For  example,  strontium  fluoride  is  used 
in  the  red  flame-arc  whose  radiant  energy  is  rich  in  red 
and  yellow.  Calcium  fluoride  is  used  in  the  carbons  of 
the  yellow  flame-arc  which  emits  excessive  red  and 
green  rays  causing  by  visual  synthesis  the  yellow 
color.  The  radiant  energy  emitted  by  the  snow-white 
flame-arc  is  a  close  approximation  to  average  daylight 
both  as  to  visible  and  to  ultra-violet  rays.  Its  carbons 
contain  rare-earths.  The  uses  of  the  flame-arcs  are 


ARTIFICIAL  LIGHT  AND  CHEMISTRY  265 


continually  being  extended  because  they  are  of  high 
intensity  and  efficiency  and  they  afford  a  variety  of 
color  or  spectral  quality.  A  million  white  flame-car¬ 
bons  are  being  used  annually  in  this  country  for  vari¬ 
ous  photochemical  processes. 

Of  the  hundreds  of  dyes  and  pigments  available  many 
are  not  permanent  and  until  recent  years  sunlight  was 
depended  upon  for  testing  the  permanency  of  coloring 
materials.  As  a  consequence  such  tests  could  not  be 
carried  out  very  systematically  until  a  powerful  arti¬ 
ficial  source  of  light  resembling  daylight  was  available. 
It  appears  that  the  white  flame-arc  is  quite  satisfactory 
in  this  field,  for  tests  indicate  that  the  chemical  effect 
of  this  arc  in  causing  dye-fading  is  four  or  five  times 
as  great  as  that  of  the  best  June  sunlight  if  the  ma¬ 
terials  are  placed  within  ten  inches  of  a  28-ampere  arc. 
It  has  been  computed  that  in  several  days  of  continuous 
operation  of  this  arc  the  same  fading  results  can  be 
obtained  as  in  a  year’s  exposure  to  daylight  in  the 
northern  part  of  this  country.  Inasmuch  as  the  fast¬ 
ness  of  colors  in  daylight  is  usually  of  interest,  the 
artificial  illuminant  used  for  color-fading  should  be 
spectrally  similar  to  daylight.  Apparently  the  white 
flame-arc  fulfils  this  requirement  as  well  as  being  a 
powerful  source. 

Lithopone,  a  white  pigment  consisting  of  zinc  sul¬ 
phide  and  barium  sulphate,  sometimes  exhibits  the 
peculiar  property  of  darkening  on  exposure  to  sunlight. 
This  property  is  due  to  an  impurity  and  apparently 
cannot  be  predicted  by  chemical  analysis.  During  the 
cloudy  days  and  winter  months  when  powerful  sunlight 
is  unavailable,  the  manufacturer  is  in  doubt  as  to  the 


266- 


ARTIFICIAL  LIGHT 


quality  of  his  product  and  he  needs  an  artificial  light- 
source  for  testing  it.  In  such  a  case  the  white  flame- 
arc  is  serving  satisfactorily,  but  it  is  not  difficult  to 
obtain  effects  with  other  light-sources  in  a  short  time 
if  an  image  of  the  light-source  is  focused  upon  the  ma¬ 
terial  by  means  of  a  lens.  In  fact,  a  darkening  of  litho- 
pone  may  be  obtained  in  a  minute  by  focusing  upon  it 
the  image  of  a  quartz  mercury-arc  by  means  of  a  quartz 
lens.  In  special  cases  of  this  sort  the  use  of  a  focused 
image  is  far  superior  to  the  ordinary  illumination  from 
the  light-source,  but,  of  course,  this  is  impracticable 
when  testing  a  large  number  of  samples  simultane¬ 
ously.  Incidentally,  lithopone  which  turns  gray  or 
nearly  black  in  the  sunlight  regains  its  whiteness  dur¬ 
ing  the  night. 

An  amusing  incident  is  told  of  a  young  man  who 
painted  his  boat  one  night  with  a  white  paint  in  which 
lithopone  was  the  pigment.  On  returning  home  the 
next  afternoon  after  the  boat  had  been  exposed  to  sun¬ 
light  all  day,  he  was  astonished  to  see  that  it  was  black. 
Being  very  much  perturbed,  he  telephoned  to  the  paint 
store,  but  the  proprietor  escaped  a  scathing  lecture  by 
having  closed  his  shop  at  the  usual  hour.  The  young 
man  telephoned  in  the  morning  and  told  the  proprietor 
what  had  happened,  but  on  being  asked  to  make  certain 
of  the  facts  he  went  to  the  window  and  looked  at  his 
boat  and  behold !  it  was  white.  It  had  regained  white¬ 
ness  during  the  night  but  would  turn  black  again  dur¬ 
ing  the  day.  Although  pigments  and  dyes  are  not  gen¬ 
erally  as  peculiar  as  lithopone,  much  uncertainty  is 
eliminated  by  systematic  tests  under  constant,  continu¬ 
ous,  and  controllable  artificial  light. 


ARTIFICIAL  LIGHT  AND  CHEMISTRY  267 


The  sources  of  so-called  chemical  rays  are  numerous 
for  laboratory  work,  but  there  is  a  need  for  highly 
efficient  powerful  producers  of  this  kind  of  energy.  In 
general,  the  flame-arcs  perhaps  are  foremost  sources 
at  the  present  time,  with  other  kinds  of  carbon  arcs  and 
the  quartz  mercury-arc  ranking  next.  One  advantage 
of  the  mercury-arc  is  its  constancy.  Furthermore,  for 
work  with  a  single  wave-length  it  is  easy  to  isolate  one 
of  the  spectral  lines.  The  regular  glass-tube  mercury- 
arc  is  an  efficient  producer  of  the  actinic  rays  and  as  a 
consequence  has  been  extensively  used  in  photographic 
work  and  in  other  photochemical  processes.  An  excel¬ 
lent  source  for  experimental  work  can  be  made  easily 
by  producing  an  arc  between  two  small  iron  rods.  The 
electric  spark  has  served  in  much  experimental  work, 
but  the  total  radiant  energy  from  it  is  small.  By 
varying  the  metals  used  for  electrodes  a  considerable 
variety  in  the  radiant  energy  is  possible.  This  is  also 
true  of  the  electric  arcs,  and  the  flame-arcs  may  be 
varied  widely  by  using  different  chemical  compounds 
in  the  carbons. 

There  are  other  effects  of  light  which  have  found  ap¬ 
plications  but  not  in  chemical  reactions.  For  example, 
selenium  changes  its  electrical  resistance  under  the  in¬ 
fluence  of  light  and  many  applications  of  this  phenome¬ 
non  have  been  made.  Another  group  of  light-effects 
forms  a  branch  of  science  known  as  photo-electricity. 
If  a  spark-gap  is  illuminated  by  ultra-violet  rays,  the 
resistance  of  the  gap  is  diminished.  If  an  insulated 
zinc  plate  is  illuminated  by  ultra-violet  or  violet  rays, 
it  will  gradually  become  positively  charged.  These 
effects  are  due  to  the  emission  of  electrons  from  the 


268 


ARTIFICIAL  LIGHT 


metal.  Violet  and  ultra-violet  rays  will  cause  a  color¬ 
less  glass  containing  manganese  to  assume  a  pinkish 
color.  The  latter  is  the  color  which  manganese  im¬ 
parts  to  glass  and  under  the  influence  of  these  rays  the 
color  is  augmented.  Certain  ultra-violet  rays  also 
ionize  the  air  and  cause  the  formation  of  ozone.  This 
can  be  detected  near  a  quartz  mercury-arc,  for  example, 
by  the  characteristic  odor. 

The  foregoing  are  only  a  few  of  the  multitude  of 
photochemical  reactions  and  other  effects  of  radiant 
energy.  The  development  of  this  field  awaits  to  some 
extent  the  production  of  so-called  actinic  rays  more 
efficiently  and  in  greater  quantities,  but  there  are  now 
many  practical  applications  of  artificial  light  for  these 
purposes.  In  the  extensive  fields  of  photography  vari¬ 
ous  artificial  light-sources  have  served  for  many  years 
and  they  are  constantly  finding  more  applications. 
Artificial  light  is  now  used  to  a  considerable  extent  in 
the  industries  in  connection  with  chemical  processes, 
but  little  information  is  available,  owing  to  the  secrecy 
attending  these  new  developments  in  industrial  proc¬ 
esses.  However,  this  brief  chapter  has  been  intro¬ 
duced  in  order  to  indicate  another  field  of  activity  in 
which  artificial  light  is  serving.  It  is  agreed  by  scien¬ 
tists  that  photochemistry  has  a  promising  future. 
Mankind  harnesses  nature’s  forces  and  produces  light 
and  this  light  is  put  to  work  to  exert  its  influence  for 
the  further  benefit  of  mankind.  Science  has  been  at 
work  systematically  for  only  a  century,  but  the  accom¬ 
plishments  have  been  so  wonderful  that  the  imagination 
dares  not  attempt  to  prophesy  the  achievements  of  the 
next  century. 


XX 


LIGHT  AND  HEALTH 

The  human  being  evolved  without  clothing  and  the 
body  was  bathed  with  light  throughout  the  day,  but 
civilization  has  gone  to  the  other  extreme  of  covering 
the  body  with  clothing  which  keeps  most  of  it  in  dark¬ 
ness.  Inasmuch  as  light  and  the  invisible  radiant 
energy  which  is  associated  with  it  are  known  to  be 
very  influential  agencies  in  a  multitude  of  ways,  the 
question  arises:  Has  this  shielding  of  the  body  had 
any  marked  influence  upon  the  human  organism?  Al¬ 
though  there  is  a  vast  literature  upon  the  subject  of 
light-therapy,  the  question  remains  unanswered,  owing 
to  the  conflicting  results  and  the  absence  of  standard¬ 
ization  of  experimental  details.  In  fact,  most  investi¬ 
gations  are  subject  to  the  criticism  that  the  data  are  in¬ 
adequate.  Throughout  many  centuries  light  has  been 
credited  with  various  influences  upon  physiological 
processes  and  upon  the  mind.  But  most  of  the  early 
applications  had  no  foundation  of  scientific  facts.  Un¬ 
fortunately,  many  of  the  claims  pertaining  to  the 
physiological  and  psychological  effects  of  light  at  the 
present  time  are  conflicting  and  they  do  not  rest  upon 
an  established  scientific  foundation.  Furthermore 
some  of  them  are  at  variance  with  the  possibilities  and 
an  unprejudiced  observer  must  conclude  that  much 
systematic  work  must  be  done  before  order  may  arise 
from  the  present  chaos.  This  does  not  mean  that  many 

269 


270 


ARTIFICIAL  LIGHT 


of  the  effects  are  not  real,  for  radiant  energy  is  known 
to  cause  certain  effects,  and  viewing  the  subject  broadly 
it  appears  that  light  is  already  serving  humanity  in 
this  held  and  that  its  future  is  promising. 

The  present  lack  of  definite  data  pertaining  to  the 
effects  of  radiation  is  due  to  the  failure  of  most  in¬ 
vestigators  to  determine  accurately  the  quantities  and 
wave-lengths  of  the  rays  involved.  For  example,  it  is 
easy  to  err  by  attributing  an  effect  to  visible  rays  when 
the  effect  may  be  caused  by  accompanying  invisible 
rays.  Furthermore,  it  may  be  possible  that  certain 
rays  counteract  or  aid  the  effective  rays  without  being 
effective  alone.  In  other  words,  the  physical  measure¬ 
ments  have  been  neglected  notwithstanding  the  fact 
that  they  are  generally  more  easily  made  than  the  de¬ 
terminations  of  curative  effects  or  of  germicidal  action. 
Radiant  energy  of  all  kinds  and  wave-lengths  has 
played  a  part  in  therapeutics,  so  it  is  of  interest  to  in¬ 
dicate  them  according  to  wave-length  or  frequency. 
These  groups  vary  in  range  of  wave-length,  but  the 
actual  intervals  are  not  particularly  of  interest  here. 
Beginning  with  radiant  energy  of  highest  frequencies 
of  vibration  and  shortest  wave-lengths,  the  following 
groups  and  subgroups  are  given  in  their  order  of  in¬ 
creasing  wave-length : 

Rontgen  or  X-rays,  which  pass  readily  through  many  sub¬ 
stances  opaque  to  ordinary  light-rays. 

Ultra-violet  rays,  which  are  divided  empirically  into  three 
groups,  designated  as  “extreme,”  “middle,”  and  “near”  in 
accordance  with  their  location  in  respect  to  the  visible  region. 

Visible  rays  producing  various  sensations  of  color,  such  as 
violet,  blue,  green,  yellow,  orange,  and  red. 


LIGHT  AND  HEALTH 


271 


Infra-red  or  the  invisible  rays  bordering  on  the  red  rays. 

An  unknown,  unmeasured,  or  unfilled  region  between  the 
infra-red  and  the  “electric’  waves. 

Electric  waves,  which  include  a  class  of  electromagnetic 
radiant  energy  of  long  wave-length.  Of  these  the  Herzian 
waves  are  of  the  shortest  wave-length  and  these  are  followed 
by  “wireless”  waves.  Electric  waves  of  still  greater  wave¬ 
length  are  due  to  the  slower  oscillations  in  certain  electric 
circuits  caused  by  lightning  discharges,  etc. 

The  Rontgen  rays  were  discovered  by  Rontgen  in 
1896  and  they  have  been  studied  and  applied  very 
widely  ever  since.  Their  great  use  has  been  in  X-ray 
photography,  but  they  are  also  being  used  in  thera¬ 
peutics.  The  extreme  ultra-violet  rays  are  not  avail¬ 
able  in  sunlight  and  are  available  only  near  a  source 
rich  in  ultra-violet  rays,  such  as  the  arc-lamps.  They 
are  absorbed  by  air,  so  that  they  are  studied  in  a 
vacuum.  These  are  the  rays  which  convert  oxygen 
into  ozone  because  the  former  strongly  absorbs  them. 
The  middle  ultra-violet  rays  are  not  found  in  sunlight, 
because  they  are  absorbed  by  the  atmosphere.  They 
are  also  absorbed  by  ordinary  glass  but  are  freety 
transmitted  by  quartz.  The  nearer  ultra-violet  rays 
are  found  in  sunlight  and  in  most  artificial  illuminants 
and  are  transmitted  by  ordinary  glass.  Next  to  this 
region  is  the  visible  spectrum  with  the  various  colors, 
from  violet  to  red,  induced  by  radiant  energy  of  in¬ 
creasing  wave-length.  The  infra-red  rays  are  some¬ 
times  called  heat-rays,  but  all  radiant  energy  may  be 
converted  into  heat.  Various  substances  transmit  and 
absorb  these  rays  in  general  quite  differently  from  the 
visible  rays.  Water  is  opaque  to  most  of  the  infra-red 


272 


ARTIFICIAL  LIGHT 


rays.  Next  there  is  a  region  of  wave-lengths  or  fre¬ 
quencies  for  which  no  radiant  energy  has  been  found. 
The  so-called  electric  waves  vary  in  wave-length  over  a 
great  range  and  they  include  those  employed  in  wire¬ 
less  telegraphy.  All  these  radiations  are  of  the  same 
general  character,  consisting  of  electromagnetic  energy, 
but  differing  in  wave-length  or  frequency  of  vibration 
and  also  in  their  effects.  In  effect  they  may  overlap 
in  many  cases  and  the  whole  is  a  chaos  if  the  physical 
details  of  quantity  and  wave-length  are  not  specified 
in  experimental  work. 

It  lias  been  conclusively  shown  that  radiant  energy 
kills  bacteria.  The  early  experiments  were  made  with 
sunlight  and  the  destruction  of  micro-organisms  is  gen¬ 
erally  attributed  to  the  so-called  chemical  rays,  namely, 
the  blue,  violet,  and  ultra-violet  rays.  It  appears  in 
general  that  the  middle  ultra-violet  rays  are  the  most 
powerful  destroyers.  It  is  certainly  established  that 
sunlight  sterilizes  water,  for  example,  and  the  quartz 
mercury-lamp  is  in  daily  use  for  this  purpose  on  a 
practicable  scale.  However,  there  still  appears  to  be  a 
difference  of  opinion  as  to  the  destructive  effect  of 
radiant  energy  upon  bacteria  in  living  tissue.  It  has 
been  shown  that  the  middle  ultra-violet  rays  destroy 
animal  tissue  and,  for  example,  cause  eye-cataracts. 
It  appears  possible  from  some  experiments  that  ultra¬ 
violet  rays  destroy  bacteria  in  water  and  on  culture 
plates  more  effectively  in  the  absence  of  visible  rays 

than  when  these  attend  the  ultra-violet  ravs  as  in  the 

«/ 

case  of  sunlight.  This  is  one  of  the  reasons  for  the  use 
of  blue  glass  in  light-therapy,  which  isolates  the  blue, 
violet,  and  near  ultra-violet  rays  from  the  other  visible 


In  art  work 


In  a  haberdashery 


JUDGING  COLOR  UNDER  ARTIFICIAL  DAYLIGHT 


In  an  underground  tunnel 


In  an  art  gallery 


ARTIFICIAL  DAYLIGHT 


LIGHT  AND  HEALTH  273 

rays.  If  the  infra-red  rays  are  not  desired  they  can 
be  readily  eliminated  by  the  nse  of  a  water-cell. 

There  is  a  vast  amount  of  testimony  which  proves 
the  bactericidal  action  of  light.  Bacteria  on  the  sur¬ 
face  of  the  body  are  destroyed  by  ultra-violet  rays. 
Typhus  and  tubercle  bacilli  are  destroyed  equally  well 
by  the  direct  rays  from  the  sun  and  from  the  electric 
arcs.  Cultures  of  diphtheria  develop  in  diffused  day¬ 
light  but  are  destroyed  by  direct  sunlight.  Lower  or¬ 
ganisms  in  water  are  readily  killed  by  the  radiation 
from  any  light-source  emitting  ultra-violet  rays  com¬ 
parable  with  those  in  direct  sunlight.  From  the  great 
amount  of  data  available  it  appears  reasonable  to  con¬ 
clude  that  radiant  energy  is  a  powerful  bactericidal 
agency  but  that  the  action  is  due  chiefly  to  ultra-violet 
rays.  It  appears  also  that  no  bacteria  can  resist  these 
rays  if  they  are  intense  enough  and  are  permitted  to 
play  upon  the  bacteria  long  enough.  The  destruction 
of  these  organisms  appears  to  be  a  phenomenon  of  ox¬ 
idation,  for  the  presence  of  oxygen  appears  to  be  neces¬ 
sary. 

The  foregoing  remarks  about  the  bactericidal  action 
of  radiant  energy  apply  only  to  bacteria  in  water,  in 
cultures,  and  on  the  surface  of  the  body.  There  is 
much  uncertainty  as  to  the  ability  of  radiant  energy  to 
destroy  bacteria  within  living  tissue.  The  active  rays 
cannot  penetrate  appreciably  into  such  tissue  and  many 
authorities  are  convinced  that  no  direct  destruction 
takes  place.  In  fact,  it  has  been  stated  that  the  so- 
called  chemical  rays  are  more  destructive  to  the  tissue 
cells  than  to  bacteria.  Finsen,  a  pioneer  in  the  use  of 
radiant  energy  in  the  treatment  of  disease,  effected 


274 


ARTIFICIAL  LIGHT 


many  wonderful  cures  and  believed  that  the  bacteria 
were  directly  destroyed  by  the  ultra-violet  rays.  How¬ 
ever,  many  have  since  come  to  the  conclusion  that  the 
beneficent  action  of  the  rays  is  due  to  the  irritation 
which  causes  an  outflow  of  serum,  thus  bringing  more 
antibodies  in  contact  with  the  bacilli,  and  causing  the 
destruction  of  the  latter.  Hot  applications  appear  to 
work  in  the  same  manner. 

Primitive  beings  of  the  tropics  are  known  to  treat 
open  wounds  by  exposing  them  to  the  direct  rays  of  the 
sun  without  dressings  of  any  kind.  These  wounds  are 
usually  infected  and  the  sun’s  rays  render  them  asep¬ 
tic  and  they  heal  readily.  Many  cases  of  sores  and 
surgical  wounds  have  been  quickly  healed  by  exposure 
to  sunlight.  Even  red  light  has  been  effective,  so  it 
has  been  concluded  by  some  that  rays  of  almost  any 
wave-length,  if  intense  enough,  will  effect  a  cure  of  this 
character  by  causing  an  effusion  of  serum.  It  has  also 
been  stated  that  the  chemical  rays  have  anaesthetic 
powers  and  have  been  used  in  this  role  for  many  minor 
operations. 

It  is  said  that  the  Chinese  have  used  red  light  for 
centuries  in  the  treatment  of  smallpox  and  throughout 
the  Middle  Ages  this  practice  was  not  uncommon.  In 
the  oldest  book  on  medicine  written  in  English  there 
is  an  account  of  a  successful  treatment  of  the  son  of 
Edward  I  for  smallpox  by  means  of  red  light.  It  is 
also  stated  that  this  treatment  was  administered 
throughout  the  reigns  of  Elizabeth  and  of  Charles  II. 
Another  account  states  that  a  few  soldiers  confined 
in  dark  dungeons  recovered  from  smallpox  without 
pitting.  Finsen  also  obtained  excellent  results  in  the 


LIGHT  AND  HEALTH 


275 


treatment  of  this  disease  by  means  of  red  light.  How¬ 
ever,  in  this  case  it  appears  that  the  exclusion  of  the 
so-called  chemical  rays  favors  healing  of  the  postules 
of  smallpox  and  that  the  use  of  red  light  is  therefore 
a  negative  application  of  light-therapy.  In  other 
words,  the  red  light  plays  no  part  except  in  furnishing 
a  light  which  does  not  inhibit  healing. 

Although  the  so-called  actinic  rays  have  curative 
value  in  certain  cases,  there  are  some  instances  where 
light-baths  are  claimed  to  be  harmful.  It  is  said  that 
sun-baths  to  the  naked  body  are  not  so  popular  as  they 
were  formerly,  except  for  obesity,  gout,  rheumatism, 
and  sluggish  metabolism,  because  it  is  felt  that  the 
shorter  ultra-violet  rays  may  be  harmful.  These  rays 
are  said  to  increase  the  pulse,  respiration,  temperature, 
and  blood-pressure  and  may  even  start  hemorrhages 
and  in  excessive  amounts  cause  headache,  palpitation, 
insomnia,  and  anemia.  These  same  authorities  con¬ 
demn  sun-baths  to  the  naked  body  of  the  tuberculous, 
claiming  that  any  cures  effected  are  consummated  de¬ 
spite  the  injury  done  by  the  energy  of  short  wave¬ 
length.  There  is  no  doubt  that  these  rays  are  beneficial 
in  local  lesions,  but  it  is  believed  that  the  cure  is  due 
to  the  irritation  caused  by  the  rays  and  the  consequent 
bactericidal  action  of  the  increased  flow  of  serum,  and 
not  to  any  direct  beneficial  result  on  the  tissue-cells. 
Others  claim  to  cure  tuberculosis  by  means  of  powerful 
quartz  mercury-arcs  equipped  with  a  glass  which  ab¬ 
sorbs  the  ultra-violet  rays  of  shorter  wave-lengths. 
These  conclusions  by  a  few  authorities  are  submitted 
for  what  they  are  worth  and  to  show  that  this  phase  of 
light-therapy  is  also  unsettled. 


276 


ARTIFICIAL  LIGHT 


Any  one  who  has  been  in  touch  with  light-therapy  in 
a  scientific  role  is  bound  to  note  that  much  ignorance  is 
displayed  in  the  use  of  light  in  this  manner.  In  fact, 
it  appears  safe  to  state  that  light-therapy  often  smacks 
of  quackery.  Very  mysterious  effects  are  sometimes 
attributed  to  radiant  energy,  which  occasionally  border 
upon  superstition.  Nevertheless,  this  kind  of  energy 
has  value,  and  notwithstanding  the  chaos  which  still 
exists,  it  is  of  interest  to  note  some  of  the  equipment 
which  has  been  used.  Some  practitioners  have  great 
confidence  in  the  electric  bath,  and  elaborate  light-baths 
have  been  devised.  In  the  earlier  years  of  this  kind  of 
treatment  the  electric  arc  was  conspicuous.  Elec¬ 
trodes  of  carbon,  carbon  and  iron,  and  iron  have  been 
used  when  intense  ultra-violet  rays  were  desired.  The 
quartz  mercury-arc  of  later  years  supplies  this  need 
admirably.  Dr.  Cleaves,  after  many  years  of  experi¬ 
ence  with  the  electric-arc  bath,  has  stated : 

From  the  administration  of  an  electric-arc  bath  there 
is  obtained  an  action  upon  the  skin,  the  patient  experi¬ 
ences  a  pleasant  and  slightly  prickly  sensation.  There 
is  produced,  even  from  a  short  exposure,  upon  the 
skin  of  some  patients  a  slight  erythema,  while  with 
others  there  is  but  little  such  effect  even  from  long 
exposures.  The  face  assumes  a  normal  rosy  coloring 
and  an  appearance  of  refreshment  and  repose  on 
emerging  from  the  bath  is  always  observed.  From  the 
administration  of  the  electric-arc  bath  there  is  also 
noted  the  establishment  of  circulatory  changes  with  a 
uniform  regulation  of  the  heart’s  action,  as  evidenced 
by  improved  volume  and  slower  pulse  rate,  the  augmen¬ 
tation  of  the  temperature,  increased  activity  of  the 
skin,  fuller  and  slower  respiration,  gradually  increased 
respiratory  capacity,  and  diminished  irritability  of 


LIGHT  AND  HEALTH 


277 


the  mucous  membrane  in  tubercular,  bronchitic,  or 
asthmatic  patients.  There  is  also  lessened  discharge  in 
those  patients  suffering  from  catarrhal  conditions  of 
the  nasal  passages.  In  diseases  of  the  respiratory 
system,  a  soothing  effect  upon  the  mucous  membranes 
is  always  experienced,  while  cough  and  expectoration 
are  diminished. 

The  cabinet  used  by  Dr.  Cleaves  was  large  enough 
to  contain  a  cot  upon  which  the  patient  reclined.  An 
arc-lamp  was  suspended  at  each  of  the  two  ends  of  the 
cabinet  and  a  flood  of  light  was  obtained  directly  and 
by  reflection  from  the  white  inside  surfaces  of  the 
cabinet.  By  means  of  mirrors  the  light  from  the  arcs 
could  be  concentrated  upon  any  desired  part  of  the 
patient. 

Finsen,  who  in  1895  published  his  observations  upon 
the  stimulating  action  of  light,  is  considered  the  pioneer 
in  the  use  of  so-called  chemical  rays  in  the  treatment  of 
disease.  He  had  a  circular  room  about  thirty-seven 
feet  in  diameter,  in  which  two  powerful  100-ampere 
arc-lamps  about  six  feet  from  the  floor  were  suspended 
from  the  ceiling.  Low  partitions  extended  radially 
from  the  center,  so  that  a  number  of  patients  could  be 
treated  simultaneously.  The  temperature  of  the  room 
was  normal,  so  that  the  treatment  was  essentially  by 
radiant  energy  and  not  by  heat.  The  chemical  action 
upon  the  skin  was  said  to  be  quite  as  strong  as  under 
sunlight.  The  exposures  varied  from  ten  minutes  to 
an  hour. 

Light-baths  containing  incandescent  filament  lamps 
are  also  used.  In  some  cases  the  lamp,  sometimes  hav¬ 
ing  a  blue  bulb,  is  merely  contained  as  a  reflector  and 


278 


ARTIFICIAL  LIGHT 


the  light  is  applied  locally  as  desired.  Light-cabinets 
are  also  used,  but  in  these  there  is  considerable  effect 
due  to  heat.  The  ultra-violet  rays  emitted  by  the  small 
electric  filament  lamps  used  in  these  cabinets  are  of 
very  low  intensity  and  the  bactericidal  action  of  the 
light  must  be  feeble.  The  glass  bulbs  do  not  transmit 
the  extreme  ultra-violet  rays  responsible  for  the  pro¬ 
duction  of  ozone,  or  the  middle  ultra-violet  rays  which 
are  effective  in  destroying  animal  tissue.  The  cabinets 
contain  from  twenty  to  one  hundred  incandescent  fila¬ 
ment  lamps  of  the  ordinary  sizes,  from  25  to  60  watts. 
In  the  days  of  the  carbon  filament  lamp  the  16-candle- 
power  lamp  was  used.  Certainly  the  heating  effect  has 
advantages  in  some  cases  over  other  methods  of  heat¬ 
ing.  The  light-rays  penetrate  the  tissue  and  are  ab¬ 
sorbed  and  transformed  into  heat.  Other  methods  in¬ 
volve  conduction  of  heat  from  the  hot  air  or  other  hot 
applications.  Of  course,  it  is  also  contended  that  the 
light-rays  are  directly  beneficial. 

Light  is  also  concentrated  upon  the  body  by  means 
of  lenses  and  mirrors.  For  this  purpose  the  sun,  the 
arc,  the  quartz  mercury-arc,  and  the  incandescent  lamp 
have  been  used.  Besides  these,  vacuum-tube  dis¬ 
charges  and  sparks  have  been  utilized  as  sources  for 
radiant  energy  and  ‘ ‘ electrical’ ’  treatment.  Rontgen 
rays  and  radium  have  also  figured  in  recent  years  in 
the  treatment  of  disease. 

The  quartz  mercury-arc  has  been  extensively  used 
in  the  past  decade  for  the  treatment  of  skin  diseases 
and  there  appears  to  be  less  uncertainty  about  the  effi¬ 
cacy  of  radiant  energy  for  the  treatment  of  surface  dis¬ 
eases  than  of  others.  Herod  related  that  the  Egyp- 


LIGHT  AND  HEALTH 


279 


tians  treated  patients  by  exposure  to  direct  sun-light 
and  throughout  the  centuries  and  among  all  types  of 
civilization  sunlight  has  been  recognized  as  having 
certain  valuable  healing  or  purifying  properties.  Fin- 
sen  in  his  early  experiments  cured  a  case  of  lupus,  a 
tuberculous  skin  disease,  by  means  of  the  visible  and 
near  ultra-violet  rays  in  sunlight.  He  demonstrated 
that  these  were  the  effective  rays  by  using  only  the 
radiant  energy  which  passed  through  a  water-cell  made 
by  using  a  convex  lens  for  each  end  of  the  cell  and  fill¬ 
ing  the  intervening  space  with  water.  This  was  really 
a  lens  made  of  glass  and  water.  The  glass  absorbed 
the  ultra-violet  rays  of  shorter  wave-length  and  the 
water  absorbed  the  infra-red  rays.  Thus  he  was  able 
to  concentrate  upon  the  diseased  skin  radiant  energy 
consisting  of  visible  and  near  ultra-violet  rays. 

The  encouraging  results  which  Finsen  obtained  in 
the  treatment  of  skin  diseases  led  him  to  become  inde¬ 
pendent  of  sunlight  by  equipping  a  special  arc-lamp 
with  quartz  lenses.  This  gave  him  a  powerful  source 
of  so-called  chemical  rays,  which  could  be  concentrated 
wherever  desired.  However,  when  science  contributed 
the  mercury-vapor  arc,  developments  were  immediately 
begun  which  aimed  to  utilize  this  artificial  source  of 
steady  powerful  ultra-violet  rays  in  liglit-therapy.  As 
a  consequence,  there  are  now  available  very  compact 
quartz  mercury-arcs  designed  especially  for  this  pur¬ 
pose.  Apparently  their  use  has  been  very  effective  in 
curing  many  skin  diseases.  Certainly  if  radiant 
energy  is  effective,  it  has  a  great  advantage  over  drugs. 
An  authority  has  stated  in  regard  to  skin  diseases 
that, 


280 


ARTIFICIAL  LIGHT 


treatment  with  the  ultra-violet  rays,  especially  in  con¬ 
junction  with  the  Rontgen  rays,  radium  and  mesotho- 
rium  is  that  treatment  which  in  most  instances  holds 
rank  as  the  first,  and  in  many  as  the  only  and  often 
enough  the  most  effective  mode  of  handling  the  dis¬ 
ease. 

Sterilization  by  means  of  the  radiation  from  the 
quartz  mercury-arc  has  been  practised  successfully  for 
several  years.  Compact  apparatus  is  in  use  for  the 
sterilization  of  water  for  drinking,  for  surgical  pur¬ 
poses,  and  for  swimming-pools,  and  the  claims  made 
by  the  manufacturers  of  the  apparatus  apparently  are 
substantiated.  One  type  of  apparatus  withstands  a 
pressure  of  one  hundred  pounds  per  square  inch  and 
may  be  connected  in  series  with  the  water-main.  The 
water  supplied  to  the  sterilizer  should  be  clear  and  free 
of  suspended  matter,  in  order  that  the  radiant  energy 
may  be  effective.  Such  apparatus  is  capable  of  steril¬ 
izing  any  quantity  of  water  up  to  a  thousand  gallons  an 
hour,  and  the  lamp  is  kept  burning  only  when  the 
water  is  flowing.  It  is  especially  useful  in  hotels, 
stores,  factories,  on  ships,  and  in  many  industries 
where  sterile  water  is  needed. 

Water  is  a  vital  necessity  in  every-day  life,  whether 
for  drinking,  cooking,  or  industrial  purposes.  It  is 
recognized  as  a  carrier  of  disease  and  the  purification 
of  water-supply  in  large  cities  is  an  important  problem. 
Chlorination  processes  are  in  use  which  render  the 
treated  water  disagreeable  to  the  taste  and  filtration 
alone  is  looked  upon  with  suspicion.  The  use  of  chemi¬ 
cals  requires  constant  analysis,  but  it  is  contended  that 

the  bactericidal  action  of  ultra-violet  ravs  is  so  certain 

*/ 


LIGHT  AND  HEALTH 


281 


and  complete  that  there  is  never  any  doubt  as  to  the 
sterilization  of  the  water  if  it  is  clear,  or  if  it  has  been 
properly  filtered  before  treating.  The  system  of 
sterilization  by  ultra-violet  rays  is  the  natural  way, 
for  the  sun’s  rays  perform  this  function  in  nature. 
Apparatus  for  sterilization  of  water  by  means  of  ultra¬ 
violet  rays  is  built  for  public  plants  in  capacities  up  to 
ten  million  gallons  per  day  and  these  units  may  be 
multiplied  to  meet  the  needs  of  the  largest  cities. 
Large  mechanical  filters  are  used  in  conjunction  with 
these  sterilizers,  and  thus  mankind  copies  nature’s 
way,  for  natural  supplies  of  pure  water  have  been  fil¬ 
tered  through  sand  and  have  been  exposed  to  the  rays 
of  the  sun  which  free  it  from  germ  life. 

Some  sterilizers  of  this  character  are  used  at  the 
place  where  a  supply  of  pure  water  is  desired  or  at  a 
point  where  water  is  bottled  for  use  in  various  parts 
of  a  factory,  hospital,  store,  or  office  building.  These 
were  used  in  some  American  hospitals  during  the  re¬ 
cent  war,  where  they  supplied  sterilized  water  for 
drinking  and  for  the  antiseptic  bathing  of  wounds.  In 
warfare  the  water  supply  is  exceedingly  important. 
For  example,  the  Japanese  in  their  campaign  in  Man¬ 
churia  boiled  the  water  to  be  used  for  drinking  pur¬ 
poses.  The  mortality  of  armies  in  many  previous  wars 
was  often  much  greater  from  preventable  diseases  than 
from  bullets,  but  the  Japanese  in  their  war  with  Russia 
reversed  the  mortality  statistics.  Of  a  total  mortality 
of  81,000  more  than  60,000  died  of  casualties  in  battle. 

The  sterilization  of  water  for  swimming-pools  is 
coming  into  vogue.  Heretofore  it  was  the  common 
practice  to  circulate  the  water  through  a  filter,  in  order 


282  ARTIFICIAL  LIGHT 

\ 

to  remove  the  impurities  imparted  to  it  by  the  bathers 
and  to  return  it  to  the  pool.  It  is  insisted  by  the  ad¬ 
herents  of  sterilization  that  filtration  of  this  sort  is 
likely  to  leave  harmful  bacteria  in  the  water.  Steril¬ 
izers  in  which  ultra-violet  rays  are  the  active  rays  are 
now  in  use  for  this  purpose,  being  connected  beyond  the 
outflow  from  the  filter.  The  effectiveness  of  the  ap¬ 
paratus  has  been  established  by  the  usual  method  of 
counting  the  bacteria.  Near  the  outlet  of  the  ordinary 
filter  a  count  revealed  many  thousand  bacteria  per 
cubic  inch  of  water  and  among  these  there  were  bac¬ 
teria  of  intestinal  origin.  Then  a  sterilizer  was  in¬ 
stalled  in  which  the  effective  elements  were  two  quartz 
mercury-lamps  which  consumed  2.2  amperes  each  at 
220  volts.  A  count  of  bacteria  in  the  water  leaving  the 
sterilizer  showed  that  these  organisms  had  been  re¬ 
duced  to  5  per  cent,  and  finally  to  a  smaller  percentage 
of  their  original  value,  and  that  all  those  of  intestinal 
origin  had  been  destroyed.  In  fact,  the  water  which 
was  returned  to  the  pool  was  better  than  that  which 
most  persons  drink.  Radiant  energy  possesses  ad¬ 
vantages  which  are  unequaled  by  other  bactericidal 
agents,  in  that  it  does  not  contaminate  or  change  the 
properties  of  the  water  in  any  way.  It  does  its  work 
of  destroying  bacteria  and  leaves  the  water  otherwise 
unchanged. 

These  glimpses  of  the  use  of  the  radiant  energy  as  a 
means  of  regaining  and  retaining  good  health  suggest 
greater  possibilities  when  the  facts  become  thoroughly 
established  and  correlated.  The  sun  is  of  primary  im¬ 
portance  to  mankind,  but  it  serves  in  so  many  ways 
that  it  is  naturally  a  compromise.  It  cannot  supply 


LIGHT  AND  HEALTH 


283 


just  the  desired  radiant  energy  for  one  purpose  and  at 
the  same  time  serve  for  another  purpose  in  the  best 
manner.  It  is  obscured  on  cloudy  days  and  disappears 
nightly.  These  absences  are  beneficial  to  some  proc¬ 
esses,  but  man  in  the  highly  organized  activity  of  pres¬ 
ent  civilization  desires  radiant  energy  of  various  quali¬ 
ties  available  at  any  time.  In  this  respect  artificial 
light  is  superior  to  the  sun  and  is  being  improved 
continually. 


XXI 

MODIFYING  ARTIFICIAL  LIGHT 


In  a  single  century  science  has  converted  the  dimly 
lighted  nights  with  their  feeble  flickering  flames  into 
artificial  daytime.  In  this  brief  span  of  years  the  pro¬ 
duction  of  light  has  advanced  far  from  the  primitive 
flames  in  use  at  the  beginning  of  the  nineteenth  cen¬ 
tury,  but,  as  has  Reen  noted  in  another  chapter,  great 
improvements  in  light-production  are  still  possible. 
Nevertheless,  the  wonderful  developments  in  the  last 
four  decades,  which  created  the  arc-lamps,  the  gas- 
mantle,  the  mercury-vapor  lamps,  and  the  series  of 
electric  incandescent-filament  lamps,  have  contributed 
much  to  the  efficiency,  safety,  health,  and  happiness  of 
mankind. 

A  hundred  years  ago  civilization  was  more  easily 
satisfied  and  an  improvement  which  furnished  more 
light  at  the  same  cost  was  all  that  could  be  desired. 
To-day  light  alone  is  not  sufficient.  Certain  kinds  of 
radiant  energy  are  required  for  photography  and  other 
photochemical  processes  and  a  vast  array  of  colored 
light  is  demanded  for  displays  and  for  effects  upon  the 
stage.  Man  now  desires  lights  of  various  colors  for 
their  expressive  effects.  He  is  no  longer  satisfied  with 
mere  light  in  adequate  quantities;  he  desires  certain 
qualities.  Furthermore,  he  no  longer  finds  it  sufficient 
to  be  independent  of  daylight  merely  in  quantity  of 
light.  In  fact,  he  has  demanded  artificial  daylight. 

284 


MODIFYING  ARTIFICIAL  LIGHT  285 


Doubtless  the  future  will  see  the  production  of  effi¬ 
cient  light  of  many  qualities  or  colors,  but  to-day  many 
of  the  demands  must  be  met  by  modifying  the  artifi¬ 
cial  illuminants  which  are  available.  Vision  is  accom¬ 
plished  entirely  by  the  distinction  of  brightness  and 
color.  An  image  of  any  scene  or  any  object  is  focused 
upon  the  retina  as  a  miniature  map  in  light,  shade,  and 
color.  Although  the  distinction  of  brightness  is  a  more 
important  function  in  vision  than  the  ability  to  distin¬ 
guish  colors,  color-vision  is  far  more  important  in  daily 
life  than  is  ordinarily  appreciated.  One  may  go 
through  life  color-blind  without  suffering  any  great  in¬ 
convenience,  but  the  divine  gift  of  color-vision  casts  a 
magical  drapery  over  all  creation.  Relatively  few  are 
conscious  of  the  wonderful  drapery  of  color,  except 
for  occasional  moments  when  the  display  is  unusual. 
Nevertheless  a  study  of  vision  in  nearly  all  crafts  re¬ 
veals  the  fact  that  the  distinction  of  colors  plays  an 
important  part. 

In  the  purchase  of  food  and  wearing-apparel,  in  the 
decoration  of  homes  and  throughout  the  arts  and  in¬ 
dustries,  mankind  depends  a  great  deal  upon  the  ap¬ 
pearance  of  colors.  He  depends  upon  daylight  in  this 
respect  and  unconsciously  often,  when  daylight  fails, 
ceases  work  which  depends  upon  the  accurate  distinc¬ 
tion  of  colors.  His  color-vision  evolved  under  day¬ 
light;  arts  and  industries  developed  under  daylight; 
and  all  his  associations  of  color  are  based  primarily 
upon  daylight.  For  these  reasons,  adequate  artificial 
illumination  does  not  make  mankind  independent  of 
daylight  in  the  practice  of  arts  and  crafts  and  in  many 
minor  activities.  In  quality  or  spectral  character,  the 


286 


ARTIFICIAL  LIGHT 


unmodified  illuminants  used  for  general  lighting  pur¬ 
poses  differ  from  daylight  and  therefore  do  not  fully 
replace  it.  Noon  sunlight  contains  all  the  spectral 
colors  in  approximately  the  same  proportions,  but  this 
is  not  true  of  these  artificial  illuminants.  For  these 
reasons  there  is  a  demand  for  artificial  daylight. 

The  “vacuum”  tube  affords  a  possibility  of  an  exten¬ 
sive  variety  of  illuminants  differing  widely  in  spectral 
character  or  color.  Every  gas  when  excited  to  lumi¬ 
nescence  by  an  electric  discharge  in  the  “vacuum”  tube 
(containing  the  gas  at  a  low  pressure)  emits  light  of  a 
characteristic  quality  or  color.  By  varying  the  gas  a 
variety  of  illuminants  can  be  obtained,  but  this  means 
of  light-production  has  not  been  developed  to  a  suffi¬ 
ciently  practicable  state  to  be  satisfactory  for  general 
lighting.  Nitrogen  yields  a  pinkish  light  and  the 
nitrogen  tube  as  developed  by  Dr.  Moore  was  in¬ 
stalled  to  some  extent  a  few  years  ago.  Neon  yields 
an  orange  light  and  has  been  used  in  a  few.  cases  for 
displays.  Carbon  dioxide  furnishes  a  white  light  sim¬ 
ilar  to  daylight  and  small  tubes  containing  this  gas  are 
in  use  to-day  where  accurate  discrimination  of  color 
is  essential. 

The  flame-arcs  afford  a  means  of  obtaining  a  va¬ 
riety  of  illuminants  differing  in  spectral  character  or 
color.  By  impregnating  the  carbons  with  various 
chemical  compounds  the  color  of  the  flame  can  be 
widely  altered.  The  white  flame-arc  obtained  by  the 
use  of  rare-earth  compounds  in  the  carbons  provides 
an  illuminant  closely  approximating  average  daylight. 
By  using  various  substances  besides  carbon  for  the 


MODIFYING  ARTIFICIAL  LIGHT 


287 


electrodes,  illuminants  differing  in  spectral  character 
can  be  obtained.  These  are  usually  rich  in  ultra-vio¬ 
let  rays  and  therefore  have  their  best  applications 
in  processes  demanding  this  kind  of  radiant  energy. 
The  arc-lamp  is  limited  in  its  application  by  its  un¬ 
steadiness,  its  bulkiness,  and  the  impracticability  of 
subdividing  it  into  light-sources  of  a  great  range  of 
luminous  intensities. 

The  most  extensive  applications  of  artificial  day¬ 
light  have  been  made  by  means  of  the  electric  incan¬ 
descent  filament  lamp,  equipped  with  a  colored  glass 
which  alters  the  light  to  the  same  quality  as  daylight. 
The  light  from  the  electric  filament  lamp  is  richer  in 
yellow,  orange,  and  red  rays  than  daylight,  and  by 
knowing  the  spectral  character  of  the  two  illuminants 
and  the  spectral  characteristics  of  colored  glasses  in 
which  various  chemicals  have  been  incorporated,  it  is 
possible  to  develop  a  colored  glass  which  will  filter 
out  of  the  excess  of  yellow,  orange,  and  red  rays  so 
that  the  transmitted  light  is  of  the  same  spectral  char¬ 
acter  as  daylight.  Thousands  of  such  artificial  day¬ 
light  units  are  now  in  use  in  the  industries,  in  stores, 
in  laboratories,  in  dye-works,  in  print-shops,  and  in 
many  other  places.  Currency  and  Liberty  Bonds  have 
been  made  under  artificial  daylight  and  such  units  are 
in  use  in  banks  for  the  detection  of  counterfeit  cur¬ 
rency.  The  diamond  expert  detects  the  color  of 
jewels  and  the  microscopist  is  certain  of  the  colors  of 
his  stains  under  artificial  daylight.  The  dyer  mixes 
his  dyes  for  the  coloring  of  tons  of  valuable  silk  and 
the  artist  paints  under  this  artificial  light.  These  are 


288 


ARTIFICIAL  LIGHT 


only  a  few  -of  a  vast  number  of  applications  of  arti¬ 
ficial  daylight,  but  they  illustrate  that  mankind  is  in¬ 
dependent  of  natural  light  in  another  respect. 

There  are  various  kinds  of  daylight,  two  of  which 
are  fairly  constant  in  spectral  character.  These  are 
noon  sunlight  and  north  skylight.  The  former  may  be 
said  to  be  white  light  and  its  spectrum  indicates  the 
presence  of  visible  radiant  energy  of  all  wave-lengths 
in  approximately  equal  proportions.  North  skylight 
contains  an  excess  of  violet,  blue,  and  blue-green  rays 
and  as  a  consequence  is  a  bluish  white.  Noon  sunlight 
on  a  clear  day  is  fairly  constant  in  spectral  character, 
but  north  skylight  varies  somewhat  depending  upon 
the  absence  or  presence  of  clouds  and  upon  the  char¬ 
acter  of  the  clouds.  If  large  areas  of  sunlit  clouds 
are  present,  the  light  is  largely  reflected  sunlight.  If 
the  sky  is  overcast,  the  north  skylight  is  a  result  of  a 
mixture  of  sunlight  and  blue  skylight  filtered  through 
the  clouds  and  is  slightly  bluish.  If  the  sky  is  clear, 
the  light  varies  from  light  blue  to  deep  blue.. 

The  daylight  which  enters  buildings  is  often  consid¬ 
erably  altered  in  color  by  reflection  from  other  build¬ 
ings  and  from  vegetation,  and  after  it  enters  a  room  it 
is  sometimes  modified  by  reflection  from  colored  sur¬ 
roundings.  It  may  be  commonly  noted  that  the  light 
reflected  from  green  grass  through  a  window  to  the  up¬ 
per  part  of  a  room  is  very  much  tinted  with  green  and 
the  light  reflected  from  a  yellow  brick  building  is  tinted 
yellow.  Besides  these  alterations,  sunlight  varies  in 
color  from  the  yellow  or  red  of  dawn  through  white  at 
noon  to  orange  or  red  at  sunset.  Throughout  the  day 
the  amount  of  light  from  the  sky  does  not  change  nearly 


FIREWORKS  AND  ILLUMINATED  BATTLE-FLEET  AT  HUDSON-FULTON  CELEBRATION 


FIREWORKS  EXHIBITION  ON  MAY  DAY  AT  PANAMA-PACIFIC  EXPOSITION 


MODIFYING  ARTIFICIAL  LIGHT  289 


as  much  as  the  amount  of  sunlight,  so  there  is  a  con¬ 
tinual  variation  in  the  proportion  of  direct  sunlight 
and  skylight  reaching  the  earth.  This  is  further  var¬ 
ied  by  the  changing  position  of  the  sun.  For  exam¬ 
ple,  at  a  north  window  in  which  the  direct  sunlight 
may  not  enter  throughout  the  day,  the  amount  of  sun¬ 
light  which  enters  by  reflection  from  adjacent  build¬ 
ings  and  other  objects  may  vary  greatly.  Thus  it  is 
seen  that  daylight  not  only  varies  in  quantity  but  also 
in  quality,  and  an  artificial  daylight,  which  is  based 
upon  an  extensive  analysis,  has  the  advantage  of  be¬ 
ing  constant  in  quantity  and  quality  as  well  as  correct 
in  quality.  Modern  artificial-daylight  units  which 
have  been  scientifically  developed  not  only  make  man¬ 
kind  independent  of  daylight  in  the  discrimination  of 
colors  but  they  are  superior  to  daylight. 

Although  there  are  many  expert  colorists  who  re¬ 
quire  an  accurate  artificial  daylight,  there  are  vast 
fields  of  lighting  where  a  less  accurate  daylight  quality 
is  necessary.  The  average  eyes  are  not  sufficiently 
skilled  for  the  finest  discrimination  of  colors  and  there¬ 
fore  the  Mazda  “ daylight’ 9  lamp  supplies  the  less  ex¬ 
acting  requirements  of  color  matching.  It  is  a  compro¬ 
mise  between  quality  and  efficiency  of  light  and  serves 
the  purpose  so  well  that  millions  of  these  lamps  have 
found  applications  in  stores,  offices,  and  industries. 
In  order  to  make  an  accurate  artificial  north  skylight 
for  color-work  by  means  of  colored  glass,  from  75  to  85 
per  cent,  of  the  light  from  a  tungsten  lamp  must  be 
filtered  out.  This  absorption  in  a  broad  sense  in¬ 
creases  the  efficiency  of  the  light,  for  the  fraction  that 
remains  is  now  satisfactory,  whereas  the  original  light 


290 


ARTIFICIAL  LIGHT 


is  virtually  useless  for  accurate  color-discrimination. 
About  one  third  of  the  original  light  is  absorbed  by  the 
bulb  of  the  tungsten  “ daylight’ ’  lamp,  with  a  resultant 
light  which  is  an  approximation  to  average  daylight. 

Old  illuminants  such  as  that  emitted  by  the  candle 
and  oil-lamp  were  used  for  centuries  in  interiors.  All 
these  illuminants  were  of  a  warm  yellow  color.  Even 
the  earlier  modern  illuminants  were  not  very  different 
in  color,  so  it  is  not  surprising  that  there  is  a  deeply 
rooted  desire  for  artificial  light  in  the  home  and  in 
similar  interiors  of  a  warm  yellow  color  simulating 
that  of  old  illuminants.  The  psychological  effect  of 
warmth  and  cheerfulness  due  to  such  illuminants  or 
colors  is  well  established.  Artificial  light  in  the  home 
symbolizes  independence  of  nature  and  protection  from 
the  elements  and  there  is  a  firm  desire  to  counteract 
the  increasing  whiteness  of  modern  illuminants  by 
means  of  shades  of  a  warm  tint.  The  white  light  is 
excellent  for  the  kitchen,  laundry,  and  bath-room,  and 
for  reading-lamps,  but  the  warm  yellow  light  is  best 
suited  for  making  cozy  and  cheerful  the  environment 
of  the  interiors  in  which  mankind  relaxes.  An  illum- 
inant  of  this  character  can  be  obtained  efficiently  by 
using  a  properly  tinted  bulb  on  tungsten  filament 
lamps.  By  absorbing  about  one  fourth  to  one  third 
of  the  light  (depending  upon  the  temperature  of  the 
filament)  the  color  of  the  candle  flame  may  be  simu¬ 
lated  by  means  of  a  tungsten  filament  lamp.  Some 
persons  are  still  using  the  carbon-filament  lamp  de¬ 
spite  its  low  efficiency,  because  they  desire  to  retain 
the  warmth  of  tint  of  the  older  illuminants.  However, 
light  from  a  tungsten  lamp  may  be  filtered  to  obtain 


MODIFYING  ARTIFICIAL  LIGHT  291 


the  same  quality  of  light  as  is  emitted  by  the  carbon 
filament  lamp  by  absorbing  from  one  fifth  to  one  fourth 
of  the  light.  The  luminous  efficiency  of  the  tungsten 
lamp  equipped  with  such  a  tinted  bulb  is  still  about 
twice  as  great  as  that  of  the  carbon-filament  lamp. 
Thus  the  high  efficiency  of  the  modern  illuminants  is 
utilized  to  advantage  even  though  their  color  is  main¬ 
tained  the  same  as  the  old  illuminants. 

All  modern  illuminants  emit  radiant  energy,  which 
does  not  affect  the  ordinary  photographic  plate.  This 
superfluous  visible  energy  merely  contributes  toward 
glare  or  a  superabundance  of  light  in  photographic 
studios.  A  glass  has  been  developed  which  transmits 
virtually  all  the  rays  that  affect  the  ordinary  photo¬ 
graphic  plate  and  greatly  reduces  the  accompanying 
inactive  rays.  Such  a  glass  is  naturally  blue  in  color, 
because  it  must  transmit  the  blue,  violet,  and  near  ul¬ 
tra-violet  rays.  Its  density  has  been  so  determined  for 
use  in  bulbs  for  the  high-efficiency  tungsten  lamps  that 
the  resultant  light  appears  approximately  the  color 
of  skylight  without  sacrificing  an  appreciable  amount 
of  the  value  of  the  radiant  energy  for  ordinary  pho¬ 
tography.  This  glass,  it  is  seen,  transmits  the  so- 
called  chemical  rays  and  is  useful  in  other  activities 
where  these  rays  alone  are  desired.  It  is  used  in  light- 
therapy  and  in  some  other  activities  in  which  the  chem¬ 
ical  effects  of  these  rays  are  utilized. 

In  the  photographic  dark-room  a  deep  red  light  is 
safe  for  all  emulsions  excepting  the  panchromatic,  and 
lamps  of  this  character  are  standard  products.  An 
orange  light  is  safe  for  many  printing  papers.  Pan¬ 
chromatic  plates  and  films  are  usually  developed  in 


292 


ARTIFICIAL  LIGHT 


the  dark  where  extreme  safety  is  desired,  but  a  very 
weak  deep  red  light  is  not  unsafe  if  used  cautiously. 
However,  many  photographic  emulsions  of  this  char¬ 
acter  are  not  very  sensitive  to  green  rays,  so  a  green 
light  has  been  used  for  this  purpose. 

A  variety  of  colored  lights  are  in  demand  for  the¬ 
atrical  effects,  displays,  spectacular  lighting,  signaling, 
etc.,  and  there  are  many  superficial  colorings  available 
for  this  purpose.  Few  of  these  show  any  appreciable 
degree  of  permanency.  Permanent  superficial  color¬ 
ings  have  recently  been  developed,  but  these  are  secret 
processes  unavailable  for  the  market.  For  this  reason 
colored  glass  is  the  only  medium  generally  available 
where  permanency  is  desired.  For  permanent  light¬ 
ing  effects,  signal  glasses,  colored  caps,  and  sheets  of 
colored  glass  may  be  used.  Tints  may  be  obtained  by 
means  of  colored  reflectors.  Other  colored  media  are 
dyes  in  lacquers  and  in  varnishes,  colored  inks,  col¬ 
ored  textiles,  and  colored  pigments. 

Inasmuch  as  colored  glass  enters  into  the  develop¬ 
ment  of  permanent  devices,  it  may  be  of  interest  to 
discuss  briefly  the  effects  of  various  metallic  com¬ 
pounds  which  are  used  in  glass.  The  exact  color  pro¬ 
duced  by  these  compounds,  which  are  often  oxides, 
varies  slightly  with  the  composition  of  the  glass  and 
method  of  manufacture,  but  this  phase  is  only  of  tech¬ 
nical  interest.  The  coloring  substances  in  glass  may 
be  divided  into  two  groups.  The  first  and  largest 
group  consists  of  those  in  which  the  coloring  matter 
is  in  true  solution;  that  is,  the  coloring  is  produced 
in  the  same  manner  as  the  coloring  of  water  in  which 
a  chemical  salt  is  dissolved.  In  the  second  group  the 


MODIFYING  ARTIFICIAL  LIGHT  293 


coloring  substances  are  present  in  a  finely  divided  or 
colloidal  state ;  that  is,  the  coloring  is  due  to  the  pres¬ 
ence  of  particles  in  mechanical  suspension.  In  gen¬ 
eral,  the  lighter  elements  do  not  tend  to  produce  col¬ 
ored  glasses,  but  the  heavier  elements  in  so  far  as  they 
can  be  incorporated  into  glass  tend  to  produce  intense 
colors.  Of  course,  there  are  exceptions  to  this  gen¬ 
eral  statement. 

The  alkali  metals,  such  as  sodium,  potassium,  and 
lithium,  do  not  color  glass  appreciably,  but  they  have 
indirect  effects  upon  the  colors  produced  by  man¬ 
ganese,  nickel,  selenium,  and  some  other  elements. 
Gold  in  sufficient  amounts  produces  a  red  in  glass  and 
in  low  concentration  a  beautiful  rose.  It  is  present  in 
the  colloidal  state.  In  the  manufacture  of  “gold”  red 
glass,  the  glass  when  first  cooled  shows  no  color,  but 
on  reheating  the  rich  ruby  color  develops.  The  glass 
is  then  cooled  slowly.  The  gold  is  left  in  a  colloidal 
state.  Copper  when  added  to  a  glass  produces  two 
colors,  blue-green  and  red.  The  blue-green  color, 
which  varies  in  different  kinds  of  glasses,  results  when 
the  copper  is  fully  oxidized,  and  the  red  by  prevent¬ 
ing  oxidation  by  the  presence  of  a  reducing  agent. 
This  red  may  be  developed  by  reheating  as  in  the  case 
of  making  gold  ruby  glass.  Selenium  produces  orange 
and  red  colors  in  glass. 

Silver  when  applied  to  the  surface  of  glass  produces 
a  beautiful  yellow  color  and  it  has  been  widely  used 
in  this  manner.  It  has  little  coloring  effect  in  glass, 
because  it  is  so  readily  reduced,  resulting  in  a  metallic 
black.  Uranium  produces  a  canary  yellow  in  soda  and 
potash-lime  glasses,  which  fluoresce,  and  these  glasses 


294 


ARTIFICIAL  LIGHT 


may  be  used  in  the  detection  of  ultra-violet  rays.  The 
color  is  topaz  in  lead  glass.  Both  sulphur  and  carbon 
are  used  in  the  manufacture  of  pale  yellow  glasses. 
Antimony  has  a  weak  effect,  but  in  the  presence  of 
much  lead  it  is  used  for  making  opaque  or  translucent 
yellow  glasses.  Chromium  produces  a  green  color, 
which  is  reddish  in  lead  glass,  and  yellowish  in  soda, 
and  potash-lime  glasses. 

Iron  imparts  a  green  or  bluish  green  color  to  glass. 
It  is  usually  present  as  an  impurity  in  the  ingredients 
of  glass  and  its  color  is  neutralized  by  adding  some 
manganese,  which  produces  a  purple  color  complement¬ 
ary  to  the  bluish  green.  This  accounts  for  the  man¬ 
ganese  purple  which  develops  from  colorless  glass  ex¬ 
posed  to  ultra-violet  rays.  Iron  is  used  in  “bottle 
green”  glass.  Its  color  is  greenish  blue  in  potash- 
lime  glass,  bluish  green  in  soda-lime  glass,  and  yellow¬ 
ish  green  in  lead  glass. 

Cobalt  is  widely  used  in  the  production  of  blue 
glasses.  It  produces  a  violet-blue  in  potash-lime  and 
soda-lime  glasses  and  a  blue  in  lead  glasses.  It  ap¬ 
pears  blue,  but  it  transmits  deep  red  rays.  For  this 
reason  when  used  in  conjunction  with  a  deep  red  glass, 
a  filter  for  only  the  deepest  red  rays  is  obtained. 
Nickel  produces  an  amethyst  color  in  potash-lime  glass, 
a  reddish  brown  in  soda-lime  glass,  and  a  purple  in 
lead  glass.  Manganese  is  used  largely  as  a  “decolor¬ 
izing”  agent  in  counteracting  the  blue-green  of  iron. 
It  produces  an  amethyst  color  in  potash-lime  glass  and 
reddish  violet  in  soda-lime  and  lead  glasses. 

These  are  the  principal  coloring  ingredients  used  in 
the  manufacture  of  colored  glass.  The  staining  of 


MODIFYING  ARTIFICIAL  LIGHT  295 


glass  is  done  under  lower  temperatures,  so  that  a 
greater  variety  of  chemical  compounds  may  be  used. 
The  resulting  colors  of  metals  and  metallic  oxides  dis¬ 
solved  in  glass  depend  not  only  upon  the  nature  of 
the  metal  used,  but  also  partly  upon  the  stage  of  oxi¬ 
dation,  the  composition  of  the  glass  and  even  upon  the 
temperature  of  the  fusion. 

In  developing  a  glass  filter  the  effects  of  the  various 
coloring  elements  are  determined  spectrally  and  the 
various  elements  are  varied  in  proper  proportions  until 
the  glass  of  desired  spectral  transmission  is  obtained. 
It  is  seen  that  the  coloring  elements  are  limited  and 
the  combination  of  these  is  further  limited  by  chemi¬ 
cal  considerations.  In  combining  various  colored 
glasses  or  various  coloring  elements  in  the  same  glass 
the  “subtractive”  method  of  color-mixture  is  utilized. 
For  example,  if  a  green  glass  is  desired,  yellowish 
green  chromium  glass  may  be  used  as  a  basis.  By  the 
addition  of  some  blue-green  due  to  copper,  the  yellow 
rays  may  be  further  subdued  so  that  the  resulting 
color  is  green. 

The  primary  colors  for  this  method  of  color-mixture 
are  the  same  as  those  of  the  painter  in  mixing  pig¬ 
ments — namely,  purple,  yellow,  and  blue-green.  Va¬ 
rious  colors  may  be  obtained  by  superposing  or  inti¬ 
mately  mixing  the  colors.  The  resulting  transmission 
(reflection  in  the  case  of  reflecting  media  such  as  pig¬ 
ments)  are  those  colors  commonly  transmitted  by  all 
the  components  of  a  mixture.  Thus, 

Purple  and  yellow  —  red 
Yellow  and  blue-green  =  green 
Blue-green  and  purple  =  blue 


296 


ARTIFICIAL  LIGHT 


The  colors  produced  by  adding  lights  are  based  not 
on  the  “subtractive”  method  but  on  the  actual  addi¬ 
tion  of  colors.  These  primaries  are  red,  green,  and 
blue  and  it  will  be  noted  that  they  are  the  complemen- 
taries  of  the  “subtractive”  primaries.  By  the  use  of 
red,  green,  and  blue  lights  in  various  proportions,  all 
colors  may  be  obtained  in  varying  degrees  of  purity. 
The  chief  mixtures  of  two  of  the  “additive”  primaries 
produce  the  “subtractive”  primaries.  Thus, 

Red  and  blue  =  purple 
Red  and  green  =  yellow 
Green  and  blue  =  blue-green 

Although  the  coloring  media  which  are  permanent 
under  the  action  of  light,  heat,  and  moisture  are  rela¬ 
tively  few,  by  a  knowledge  of  their  spectral  character¬ 
istics  and  other  principles  of  color  the  expert  is  able 
to  produce  many  permanent  colors  for  lighting  effects. 
The  additive  and  subtractive  methods  are  chiefly  in¬ 
volved,  but  there  is  another  method  which  is  an  “  aver¬ 
aging”  additive  one.  For  example,  if  a  warm  tint  of 
yellow  is  desired  and  only  a  dense  yellow  glass  is  avail¬ 
able,  the  yellow  glass  may  be  cut  into  small  pieces  and 
arranged  upon  a  colorless  glass  in  checker-board  fash¬ 
ion.  Thus  a  great  deal  of  uncolored  light  which  is 
transmitted  by  the  filter  is  slightly  tinted  by  the  yel¬ 
low  light  passing  through  the  pieces  of  yellow  glass. 
If  this  light  is  properly  mixed  by  a  diffusing  glass  the 
effect  is  satisfactory.  These  are  the  principal  means 
of  obtaining  colored  light  by  means  of  filters  and  by 
mixing  colored  lights.  By  using  these  in  conjunction 
with  the  array  of  light-sources  available  it  is  possible 


MODIFYING  ARTIFICIAL  LIGHT  297 


to  meet  most  of  the  growing  demands.  Of  course,  the 
ideal  solution  is  to  make  the  colored  light  directly  at 
the  light-source,  and  doubtless  future  developments 
which  now  appear  remote  or  even  impossible  will  sup¬ 
ply  such  colored  illuminants.  In  the  meantime,  much 
is  being  accomplished  with  the  means  available. 


XXII 


SPECTACULAR  LIGHTING 

Artificial  light  is  a  natural  agency  for  producing 
spectacular  effects.  It  is  readily  controlled  and  al¬ 
tered  in  color  and  the  brightness  which  it  lends  to  dis¬ 
plays  outdoors  at  night  renders  them  extremely  con¬ 
spicuous  against  the  darkness  of  the  sky.  It  sur¬ 
passes  other  decorative  media  by  the  extreme  range 
of  values  which  may  be  obtained.  The  decorator  and 
painter  are  limited  by  a  range  of  values  from  black  to 
white  pigments,  which  ordinarily  represents  an  ex¬ 
treme  contrast  of  about  one  to  thirty.  The  bright¬ 
nesses  due  to  light  may  vary  from  darkness  to  those 
of  the  light-sources  themselves.  The  decorator  deals 
with  secondary  light — that  is,  light  reflected  by  more 
or  less  diffusely  reflecting  objects.  The  lighting  expert 
has  at  his  command  not  only  this  secondary  light  but 
the  primary  light  of  the  sources.  Lighting  effects 
everywhere  attract  attention  and  even  the  modern  mer¬ 
chant  testifies  that  adequate  lighting  in  his  store  is 
of  advertising  value.  In  all  the  field  of  spectacular 
lighting  the  superiority  of  artificial  light  over  natural 
light  is  demonstrated. 

Light  is  a  universal  medium  with  which  to  attract 
attention  and  to  enthrall  mankind.  The  civilizations 
of  all  ages  have  realized  this  natural  power  of  light. 
It  has  played  a  part  in  the  festivals  and  triumphal  pro- 

298 


SPECTACULAR  LIGHTING 


299 


cessions  from  time  immemorial  and  is  still  the  most 
important  feature  of  many  celebrations.  In  the  early 
festivals  fires,  candles,  and  oil-lamps  were  used  and 
fireworks  were  invented  for  the  purpose.  Even  to-day 
the  pyrotechnical  displays  against  the  dark  depths  of 
the  night  sky  hold  mankind  spellbound.  But  these 
evanescent  notes  of  light  have  been  improved  upon  by 
more  permanent  displays  on  a  huge  scale.  Thirty 
years  before  the  first  practical  installation  of  gas-light¬ 
ing  an  exhibition  of  4 4 Philosophical  Fireworks”  pro¬ 
duced  by  the  combustion  of  inflammable  gases  was 
given  in  several  cities  of  England. 

It  is  a  long  step  from  the  array  of  flickering  gas- 
flames  with  which  the  fronts  of  the  buildings  of  the 
Soho  works  were  illuminated  a  century  ago  to  the  won¬ 
derful  lighting  effects  a  century  later  at  the  Panama- 
Pacific  Exposition.  Some  who  saw  that  original  dis¬ 
play  of  gas-jets  totaling  a  few  hundred  candle-power 
described  it  as  an  “occasion  of  extraordinary  splen¬ 
dour.”  What  would  they  have  said  of  the  modern 
spectacular  lighting  at  the  Exposition  where  Ryan  used 
in  a  single  effect  forty-eight  large  search-lights  aggre¬ 
gating  2,600,000,000  beam  candle-power!  No  other 
comparison  exemplifies  more  strikingly  the  progress 
of  artificial  lighting  in  the  hundred  years  which  have 
elapsed  since  it  began  to  be  developed. 

The  nature  of  the  light-sources  in  the  first  half  of 
the  nineteenth  century  did  not  encourage  spectacular 
or  display  lighting.  In  fact,  this  phase  of  lighting 
chiefly  developed  along  with  electric  lamps.  Of 
course,  occasionally  some  temporary  effect  was  at¬ 
tempted  as  in  the  case  of  illuminating  the  dome  of  St. 


300 


ARTIFICIAL  LIGHT 


Paul’s  Cathedral  in  London  in  1872,  but  continued 
operation  of  the  display  was  not  entertained.  In  the 
case  of  lighting  this  dome  a  large  number  of  ship’s 
lanterns  were  used,  but  the  result  was  unsatisfactory. 
After  this  unsuccessful  attempt  at  lighting  St.  Paul’s, 
a  suggestion  was  made  of  1  i  flooding  it  with  electric 
light  projected  from  various  quarters.”  Spectacular 
lighting  outdoors  really  began  in  earnest  in  the  dawn 
of  the  twentieth  century. 

Although  some  of  the  first  attempts  at  spectacular 
lighting  outdoors  were  made  with  search-lights,  spec¬ 
tacular  lighting  did  not  become  generally  popular  until 
the  appearance  of  incandescent  filament  lamps  of  rea¬ 
sonable  efficiency  and  cost.  The  effects  were  obtained 
primarily  by  the  use  of  small  electric  filament  lamps 
draped  in  festoons  or  installed  along  the  outlines  and 
other  principal  lines  of  buildings  and  monuments. 
The  effect  was  almost  wholly  that  of  light,  for  the  glare 
from  the  visible  lamps  obscured  the  buildings  or  other 
objects.  The  method  is  still  used  because  it  is  simple 
and  the  effects  may  be  permanently  installed  without 
requiring  any  attention  excepting  to  replace  burned- 
out  lamps.  However,  the  method  has  limitations  from 
an  artistic  point  of  view  because  the  artistic  effects  of 
painting,  sculpture,  and  architecture  cannot  be  com¬ 
bined  with  it  very  effectively.  For  example,  the  de¬ 
tails  of  a  monument  or  of  a  building  cannot  be  seen 
distinctly  enough  to  be  appreciated.  The  effect  is 
merely  that  of  outlines  or  lines  and  patterns  of  points 
of  light  and  is  usually  glaring. 

The  next  step  was  to  conceal  these  lamps  behind  the 
cornices  or  other  projections  or  in  nooks  constructed 


SPECTACULAR  LIGHTING 


301 


for  the  purpose.  Light  now  began  to  mold  and  to 
paint  the  objects.  The  structures  began  to  be  visi¬ 
ble;  at  least  the  important  cornices  and  other  details 
were  no  longer  mere  outlines.  The  introduction  of  the 
drawn-wire  tungsten  lamp  is  responsible  for  an  innova¬ 
tion  in  spectacular  lighting  of  this  sort,  for  now  it  be¬ 
came  possible  to  make  concentrated  light-sources  so 
essential  to  projectors.  Furthermore,  these  lighting 
units  require  very  little  attention  after  once  being 
located.  With  the  introduction  of  electric-filament 
lamps  of  this  character  small  projectors  came  into  use, 
and  by  means  of  concentrated  beams  of  light  whole 
buildings  and  monuments  could  be  flooded  with  light 
from  remote  positions.  The  effects  obtained  by  con¬ 
cealing  lamps  behind  cornices  had  demonstrated  that 
the  lighting  of  the  surfaces  was  the  object  to  be  real¬ 
ized  in  most  cases,  and  when  small  projectors  not  re¬ 
quiring  constant  attention  became  available,  a  great 
impetus  was  given  to  flood-lighting. 

When  France  gave  to  this  country  the  Bartholdi 
Statue  of  Liberty  there  was  no  thought  of  having  this 
emblem  visible  at  night  excepting  for  the  torch  held 
in  the  hand  of  Liberty.  This  torch  was  modified  at 
the  time  of  the  erection  of  the  statue  to  accommodate 
the  lamps  available,  with  the  result  that  it  was  merely 
a  lantern  containing  a  number  of  electric  lamps.  At 
night  it  was  a  speck  of  light  more  feeble  than  many 
surrounding  shore  lights.  The  statue  had  been  lighted 
during  festivals  with  festoons  and  outlines  of  lamps, 
but  in  1915,  when  the  freedom  of  the  generous  donor 
of  the  statue  appeared  to  be  at  stake,  a  movement  was 
begun  which  culminated  in  a  fund  for  flood-lighting 


302 


ARTIFICIAL  LIGHT 


Liberty.  The  broad  foundation  of  the  statue  made  the 
lighting  comparatively  easy  by  means  of  banks  of  in¬ 
candescent  filament  search-lights.  About  225  of  these 
units  were  used  with  a  total  beam  candle-power  of 
about  20,000,000.  The  original  idea  of  an  imitation 
flame  for  the  torch  was  restored  by  building  this  from 
pieces  of  yellow  cathedral  glass  of  three  densities. 
About  six  hundred  pieces  of  glass  were  used,  the  upper 
ones  being  generally  of  the  lighter  tints  and  the  lower 
ones  of  the  darker  tints.  A  lighthouse  lens  was  placed 
in  this  lantern  so  that  an  intense  beam  of  light  would 
radiate  from  it.  The  flood-lighted  Statue  of  Liberty 
is  now  visible  by  night  as  well  as  by  day  and  it  has 
a  double  significance  at  night,  for  light  also  symbolizes 
independence. 

Just  as  the  Statue  of  Liberty  stands  alone  in  the 
New  York  Harbor  so  does  the  Wool  worth  Building 
reign  supreme  on  lower  Manhattan.  Liberty  proclaims 
independence  from  the  bondage  of  man  and  the  Wool- 
worth  Tower  stands  majestically  in  defiance  of  the 
elements  as  a  symbol  of  man’s  growing  independence 
of  nature.  This  building  with  its  cream  terra-cotta 
surface  and  intricate  architectural  details  touched  here 
and  there  with  buff,  blue,  green,  red,  and  gold,  rises  792 
feet  or  sixty  stories  above  the  street  and  typifies  the 
American  spirit  of  conceiving  and  of  executing  great 
undertakings.  In  it  are  blended  art,  utility,  and  maj¬ 
esty.  Viewed  by  multitudes  during  the  day,  it  is  a 
valuable  advertisement  for  the  name  which  stands  for 
a  national  institution.  But  by  day  it  shares  attention 
with  its  surroundings.  If  lighted  at  night  it  would 
stand  virtually  alone  against  the  dark  sky  and  the 


SPECTACULAR  LIGHTING  303 

investment  would  not  be  wholly  idle  during  the  evening 
hours. 

Mr.  H.  H.  Magdsick,  who  designed  the  lighting  for 
Liberty,  planned  the  lighting  for  the  Woolworth 
Tower,  which  rises  407  feet  or  thirty-one  stories  above 
the  main  building.  Five  hundred  and  fifty  projectors 
containing  tungsten  filament  lamps  were  distributed 
about  the  base  of  the  tower  and  among  some  of  the 
architectural  details.  The  main  architectural  features 
of  the  mansard  roof  extending  from  the  fifty-third  to 
the  fifty-seventh  floor,  the  observation  balcony  at  the 
fifty-eighth  and  the  lantern  structures  at  the  fifty- 
ninth  and  sixtieth  floors  are  covered  with  gold-leaf. 
By  proper  placing  of  the  projectors  a  glittering  effect 
is  obtained  from  these  gold  surfaces.  The  crowning 
features  of  the  lighting  effect  are  the  lanterns  in  the 
crest  of  the  spire.  Twenty-four  1000-watt  tungsten 
lamps  were  placed  behind  crystal  diffusing  glass,  which 
transmits  the  light  predominantly  in  a  horizontal  direc¬ 
tion.  Thus  at  long  distances,  from  which  the  archi¬ 
tectural  details  cannot  be  distinguished,  the  brilliant 
crowning  light  is  visible.  An  automatic  dimmer  was 
devised  so  that  the  effect  of  a  huge  varying  flame  was 
obtained.  At  close  range,  owing  to  the  nature  of  the 
glass  panels,  this  portion  is  not  much  brighter  than  the 
remainder  of  the  surfaces.  When  the  artificial  light¬ 
ing  is  in  operation  the  tower  becomes  a  majestic  spire 
of  light  and  this  magnificent  Gothic  structure  project¬ 
ing  defiantly  into  the  depths  of  darkness  is  in  more 
than  one  sense  a  torch  of  modern  civilization. 

Many  prominent  buildings  and  monuments  have 
burst  forth  in  a  flood  of  light,  and  their  beauty  and 


304 


ARTIFICIAL  LIGHT 


symbolism  have  been  appreciated  at  night  by  many 
persons  who  do  not  notice  them  by  day.  Not  only  are 
the  beautiful  structures  of  man  lighted  permanently 
but  many  temporary  effects  are  devised.  Artificial 
lighting  effects  have  become  a  prominent  part  in  out¬ 
door  festivals,  pageants,  and  theatricals.  Candles 
have  been  associated  with  Christmas  trees  ever  since 
the  latter  came  into  use  and  naturally  artificial  light 
has  been  a  feature  in  the  community  Christmas  trees 
which  have  come  into  vogue  in  recent  years.  The 
Municipal  Christmas  Tree  in  Chicago  in  1916  was 
ninety  feet  high  and  was  lighted  with  projectors. 
Thousands  of  gems  taken  from  the  Tower  of  Jewels  at 
the  San  Francisco  Exposition  added  life  and  sparkle 
to  that  of  the  other  decorations. 

After  the  close  of  the  recent  war  artificial  light 
played  a  prominent  part  throughout  the  country  in  the 
joyful  festivals.  A  jeweled  arch  erected  in  New  York 
in  honor  of  the  returning  soldiers  rivaled  some  of  the 
spectacles  of  the  Panama-Pacific  Exposition.  The 
arch  hung  like  a  gigantic  curtain  of  jewels  between  two 
obelisks,  which  rose  to  a  height  of  eighty  feet  and  were 
surmounted  by  jeweled  forms  in  the  shape  of  sunbursts. 
Approximately  thirty  thousand  jewels  glittered  in  the 
beams  of  batteries  of  arc-projectors.  Many  of  the 
signs  and  devices  which  played  a  part  in  the  “Welcome 
Home”  movement  were  of  striking  nature  and  of  a 
character  to  indicate  permanency.  The  equipment  of 
a  large  building  consisted  of  more  than  five  thousand 
10-watt  lamps,  the  entire  building  being  outlined  with 
stars  consisting  of  eleven  lamps  each.  The  “Brighten 
Up”  campaign  spread  throughout  the  country.  The 


The  Capitol  flooded  with  light 


Luna  Park,  Coney  Island,  studded  with  60,000  incandescent  filament  lamps 


THE  NEW  FLOOD  LIGHTING  CONTRASTED  WITH  THE  OLD  OUTLINE 

LIGHTING 


NIAGARA  FALLS  FLOODED  WITH  LIGHT 


SPECTACULAR  LIGHTING 


305 


lighting  and  installation  of  signs  and  special  patriotic 
displays,  the  flooding  of  streets  and  shop-windows 
with  light  without  stint,  produced  an  inspiring  and 
uplifting  effect  which  did  much  to  restore  cheerfulness 
and  optimism.  A  glowing  example  was  set  in  Wash¬ 
ington,  where  the  flood-lighting  of  the  Capitol,  discon¬ 
tinued  shortly  after  our  entrance  into  the  war,  was 
resumed. 

In  Chicago  a  “Victory  Way”  was  established,  with 
street-lighting  posts  on  both  sides  of  the  street 
equipped  with  red,  white,  and  blue  globes  surmounted 
by  a  golden  goddess  of  Victory.  One  hundred  and 
seventy-five  projectors  were  installed  along  the  way  on 
the  roofs  and  in  the  windows  of  office  buildings.  A 
brilliant,  scintillating  “Altar  of  Victory”  was  erected 
at  the  center  of  the  Way.  It  was  composed  of  two 
enormous  candelabra  erected  one  on  each  side  of  a 
platform  ninety  feet  high.  These  were  studded  with 
jewels  and  supported  a  curtain  of  jewels  suspended 
from  the  altar.  In  the  center  of  the  curtain  was  a 
huge  jeweled  eagle  bearing  the  Allied  flags.  This  was 
illuminated  by  arc-projectors  which  delivered  200,000,- 
000  beam  candle-power.  In  addition  to  these  there 
were  many  smaller  projectors.  In  the  top  of  each 
candelabra  six  large  red-and-orange  lamps  were  in¬ 
stalled  in  reflectors.  These  illuminated  live  steam 
which  issued  from  the  top.  Surmounting  the  whole 
was  a  huge  luminous  fan  formed  by  beams  from  large 
arc  search-lights.  These  are  only  a  few  of  the  many 
lighting  effects  which  welcomed  the  returning  soldiers, 
but  they  illustrate  how  much  modern  civilization  de¬ 
pends  upon  artificial  light  for  expressing  its  feelings 


306 


ARTIFICIAL  LIGHT 


and  emotions.  Throughout  all  these  festivals  light 
silently  symbolized  happiness,  freedom,  and  advance¬ 
ment. 

Projectors  were  used  on  a  large  scale  in  several 
cases  before  the  advent  of  the  concentrated  filament 
lamp.  W.  D*A.  Ryan,  the  leader  in  spectacular  light¬ 
ing,  lighted  the  Niagara  Falls  in  1907  with  batteries 
of  arc-projectors  aggregating  1,115,000,000-beam  can¬ 
dle-power.  In  1908  he  used  thirty  arc-projectors  to 
flood  the  Singer  Tower  in  New  York  with  light  and 
projected  light  to  the  flag  on  top  by  means  of  a  search¬ 
light  thirty  inches  in  diameter.  Many  flags  waved 
throughout  the  war  in  the  beams  of  search-lights,  sym¬ 
bolizing  a  patriotism  fully  aroused.  The  search-light 
beam  as  it  bores  through  the  atmosphere  at  night  is 
usually  faintly  bright,  owing  to  the  small  amount  of 
fog,  dust,  and  smoke  in  the  air.  By  providing  more 
4  ‘  substance  ’  ’  in  the  atmosphere,  the  beams  are  made  to 
appear  brighter.  Following  this  reasoning,  Ryan  de¬ 
veloped  his  scintillator  consisting  of  a  battery  of 
search-light  beams  projected  upward  through  clouds  of 
steam  which  provided  an  artificial  fog.  This  was  first 
displayed  at  the  Hudson-Fulton  celebration  with  a 
battery  of  arc  search-lights  totaling  1,000,000,000- 
candle-power. 

All  these  effects  despite  their  magnitude  were 
dwarfed  by  those  at  the  Panama-Pacific  Exposition, 
and  inasmuch  as  this  up  to  the  present  time  represents 
the  crowning  achievement  in  spectacular  lighting,  some 
of  the  details  worked  out  by  Ryan  may  be  of  interest. 
In  general,  the  lighting  effects  departed  from  the 
bizarre  outline  lighting  in  which  glaring  light-sources 


SPECTACULAR  LIGHTING* 


307 


studded  the  structures.  The  radiant  grandeur  and 
beauty  of  flood-lighting  from  concealed  light-sources 
was  the  key-note  of  the  lighting.  In  this  manner  won¬ 
derful  effects  were  obtained,  which  not  only  appealed  to 
the  eye  and  to  the  artistic  sensibility  but  which  were 
free  from  glare.  By  means  of  flood-lighting  and  relief  - 
lighting  from  concealed  light-sources  the  third  dimen¬ 
sion  or  depth  was  obtained  and  the  architectural  de¬ 
tails  and  colorings  were  preserved.  A  great  many  dif¬ 
ferent  kinds  of  devices  and  lamps  were  used  to  make 
the  night  effects  superior  in  grandeur  to  those  of  day¬ 
time.  The  Zone  or  amusement  section  was  lighted  with 
bare  lamps  in  the  older  manner  and  the  glaring  bizarre 
effects  contrasted  the  spectacular  lighting  of  the  past 
with  the  illumination  of  the  future. 

In  another  section  the  visitor  was  greeted  with  a 
gorgeous  display  of  carnival  spirit.  Beautifully  col¬ 
ored  heraldic  shields  on  which  were  written  the  early 
history  of  the  Pacific  coast  were  illuminated  by  groups 
of  luminous  arc-lamps  on  standards  varying  from 
twenty-five  to  fifty-five  feet  in  height.  The  Tower  of 
Jewels  with  more  than  a  hundred  thousand  dangling 
gems  was  flood-lighted,  and  the  myriads  of  minute  re¬ 
flected  images  of  light-sources  glittering  against  the 
dark  sky  produced  an  effect  surpassing  the  dreams  of 
imagination.  Shadows  and  high-lights  of  striking 
contrasts  or  of  elusive  colors  greeted  the  visitor  on 
every  hand.  Individual  isolated  effects  of  light  were 
to  be  found  here  and  there.  Fire  hissed  from  the 
mouths  of  serpents  and  cast  the  spell  of  mobile  light 
over  the  composite  Spanish-Gothic-Oriental  setting. 
A  colored  beam  of  a  search-light  played  here  and  there. 


308 


ARTIFICIAL  LIGHT 


Mysterious  vapors  rising  from  caldrons  were  in  real¬ 
ity  illuminated  steam.  Symbolic  fountain  groups  did 
not  escape  the  magic  touch  of  the  lighting  wizard. 

In  the  Court  of  the  Universe  great  areas  were  illu¬ 
minated  by  two  fountains  rising  about  a  hundred  feet 
above  the  sunken  gardens.  One  of  these  symbolized 
the  setting  sun,  the  other  the  rising  sun.  The  shaft 
and  ball  at  the  crest  of  each  fountain  were  glazed  with 
heavy  opal  glass  imitating  travertine  marble  and  in 
these  were  installed  incandescent  lamps  of  a  total  can¬ 
dle-power  of  500,000.  The  balustrade  seventy  feet 
above  the  sunken  gardens  was  surmounted  by  nearly 
two  hundred  incandescent  filament  search-lights. 
Light  was  everywhere,  either  varying  in  color  into  a 
harmonious  scene  or  changing  in  light  and  shadow  to 
mold  the  architecture  and  sculpture.  The  enormous 
glass  dome  of  the  Palace  of  Horticulture  was  converted 
into  an  astronomical  sphere  by  projecting  images  upon 
it  in  such  a  manner  that  spots  of  light  revolved ;  rings 
and  comets  which  appeared  at  the  horizon  passed  on 
their  way  through  the  heavens,  changing  in  color  and 
disappearing  again  at  the  horizon.  All  these  effects 
and  many  more  were  mirrored  in  the  waters  of  the 
lagoons  and  the  whole  was  a  Wonderland  indeed. 

The  scintillator  consisted  of  48  arc  search-lights 
three  feet  in  diameter  totaling  2,600,000,000  beam  can¬ 
dle-power.  The  lighting  units  were  equipped  with 
colored  screens  and  the  beams  which  radiated  upward 
were  supplied  with  an  artificial  fog  by  means  of  steam 
generated  by  a  modern  express  locomotive.  The  latter 
was  so  arranged  that  the  wheels  could  be  driven  at  a 
speed  of  sixty  miles  per  hour  under  brake,  thereby 


SPECTACULAR  LIGHTING 


309 


emitting  great  volumes  of  steam  and  smoke,  which 
when  illuminated  with  various  colors  produced  a  mag¬ 
nificent  spectacle.  Over  three  hundred  scintillator 
effects  were  worked  out  and  this  feature  of  tireless  fire¬ 
works  was  widely  varied.  The  aurora  borealis  and 
other  effects  created  by  this  battery  of  search-lights 
extended  for  many  miles.  The  many  effects  regularly 
available  were  augmented  on  special  occasions  and  it 
is  safe  to  state  that  this  apparatus  built  upon  a  huge 
scale  provided  a  flexibility  of  tireless  fireworks  never 
attained  even  with  small-scale  devices. 

The  lighting  of  the  exposition  can  barely  be  touched 
upon  in  a  few  paragraphs  and  it  would  be  difficult  to 
describe  in  words  even  if  space  were  unlimited.  It 
represented  the  power  of  light  to  beautify  and  to  awe. 
It  showed  the  feebleness  of  the  decorator’s  media  in 
comparison  with  light  pulsating  with  life.  It  consisted 
of  a  great  variety  of  direct,  masked,  concealed,  and  pro¬ 
jected  effects,  but  these  were  blended  harmoniously 
with  one  another  and  with  the  decorative  and  architec¬ 
tural  details  of  the  structures.  It  was  a  crowning 
achievement  of  a  century  of  public  lighting  which  be¬ 
gan  with  Murdock’s  initial  display  of  a  hundred  flicker¬ 
ing  gas-jets.  It  demonstrated  the  powers  of  science 
in  the  production  of  light  and  of  genius  and  imagina¬ 
tion  in  the  utilization  of  light.  It  was  a  silent  but  pul¬ 
sating  display  of  grandeur  dwarfing  into  insignificance 
the  aurora  borealis  in  its  most  resplendent  moments. 


XXIII 


THE  EXPRESSIVENESS  OF  LIGHT 

From  an  esthetic  or,  more  broadly,  a  psychological 
point  of  view  no  medium  rivals  light  in  expressiveness. 
Not  only  is  light  allied  with  man’s  most  important 
sense  but  throughout  long  ages  of  associations  and  uses 
mankind  has  bestowed  upon  it  many  attributes.  In 
fact,  it  is  possible  that  light,  color,  and  darkness  pos¬ 
sess  certain  fundamentally  innate  powers;  at  least, 
they  have  acquired  expressive  and  impressive  powers 
through  the  many  associations  in  mythology,  religion, 
nature,  and  common  usage.  Besides  these  attributes, 
light  possesses  a  great  advantage  over  the  media  of 
decoration  in  obtaining  brightness  and  color  effects. 
For  example,  the  landscape  artist  cannot  reproduce  the 
range  of  values  or  brightnesses  in  most  of  nature’s 
scenes,  for  if  black  is  used  to  represent  a  deep 
shadow,  white  is  not  bright  enough  to  represent  the 
value  of  the  sky.  In  fact,  the  range  of  brightnesses 
represented  by  the  deep  shadow  and  the  sky  extends 
far  beyond  the  range  represented  by  black  and  white 
pigments.  The  extreme  contrast  ordinarily  available 
by  means  of  artist’s  colors  is  about  thirty  to  one,  but 
the  sky  is  a  thousand  times  brighter  than  a  shadow,  a 
sunlit  cloud  is  thousands  of  times  brighter  than  the 
deep  shadows  of  woods,  and  the  sun  is  millions  of  times 
brighter  than  the  shadows  in  a  landscape. 

310 


THE  EXPRESSIVENESS  OF  LIGHT  311 


The  range  of  brightnesses  obtainable  by  means  of 
light  extends  from  darkness  or  black  throughout  the 
range  represented  by  pigments  under  equal  illumina¬ 
tion  and  beyond  these  through  the  enormous  range  ob¬ 
tainable  by  unequal  illumination  of  surfaces  to  the 
brightnesses  of  the  light-sources  themselves.  In  the 
matter  of  purity  of  colors,  light  surpasses  reflecting 
media,  for  it  is  easy  to  obtain  approximately  pure  hues 
by  means  of  light  and  to  obtain  pure  spectral  hues  by 
resorting  to  the  spectrum  of  light.  It  is  impossible  to 
obtain  pure  hues  by  means  of  pigments  or  of  other 
reflecting  media.  These  advantages  of  light  are  very 
evident  on  turning  to  spectacular  lighting  effects,  and 
even  the  lighting  of  interiors  illustrates  a  potentiality 
in  light  superior  to  other  media.  For  example,  in  a 
modern  interior  in  which  concealed  lighting  produces 
brilliantly  illuminated  areas  above  a  cornice  and  dark 
shadows  on  the  under  side,  the  range  in  values  is  often 
much  greater  than  that  represented  by  black  and  white, 
and  still  there  remains  the  possibility  of  employing  the 
light-sources  themselves  in  extending  the  scale  of 
brightness.  Superposing  color  upon  the  whole  it  is 
obvious  that  the  combination  of  “primary”  light  with 
reflected  light  possesses  much  greater  potentiality  than 
the  latter  alone.  This  potentiality  of  light  is  best  real¬ 
ized  if  lighting  is  regarded  as  “painting  with  light” 
in  a  manner  analogous  to  the  decorator’s  painting  with 
pigments,  etc. 

The  expressive  possibilities  of  lighting  find  extensive 
applications  in  relation  to  painting,  sculpture,  and 
architecture.  A  painting  is  an  expression  of  light  and 
the  sculptor’s  product  finally  depends  upon  lighting  for 


312 


ARTIFICIAL  LIGHT 


its  effectiveness.  Lighting  is  the  master  painter  and 
sculptor.  It  may  affect  the  values  of  a  painting  to 
some  extent  and  it  is  a  great  influence  upon  the  colors. 
It  molds  the  model  from  which  the  sculptor  works  and 
it  molds  the  completed  work.  The  direction,  distribu¬ 
tion,  and  quality  of  light  influence  the  appearance  of  all 
objects  and  groups  of  them.  Aside  from  the  modeling 
of  ornament,  the  light  and  shade  effects  of  relatively 
large  areas  in  an  interior  such  as  walls  and  ceiling,  the 
contrasts  in  the  brightnesses  of  alcoves  with  that  of 
the  main  interior,  and  the  shadows  under  cornices, 
beams,  and  arches  are  expressions  of  light. 

The  decorator  is  able  to  produce  a  certain  mood  in  a 
given  interior  by  varying  the  distribution  of  values  and 
the  choice  of  colors  and  the  lighting  artist  is  able  to  do 
likewise,  but  the  latter  is  even  able  to  alter  the  mood 
produced  by  the  decorator.  For  example,  a  large  in¬ 
terior  flooded  with  light  from  concealed  sources  has  the 
airiness  and  extensiveness  of  outdoors.  If  lighted 
solely  by  means  of  sources  concealed  in  an  upper  cor¬ 
nice,  the  ceiling  may  be  bright  and  the  walls  may  be 
relatively  dark  by  contrast.  Such  a  lighting  effect  may 
produce  a  feeling  of  being  hemmed  in  by  the  walls 
without  a  roof.  If  the  room  is  lighted  by  means  of 
chandeliers  hung  low  and  equipped  with  shades  in  such 
a  manner  that  the  lower  portions  of  the  walls  may  be 
light  while  the  upper  portions  of  the  interior  may  be 
ill  defined,  the  feeling  produced  may  be  that  of  being 
hemmed  in  by  crowding  darkness.  Thus  lighting  is 
productive  of  moods  and  illusions  ranging  from  the 
mystery  of  crowding  darkness  to  the  extensiveness  of 
outdoors. 


THE  EXPRESSIVENESS  OF  LIGHT  313 


Future  lighting  of  interiors  doubtless  will  provide  an 
adequacy  of  lighting  effects  which  will  meet  the  re¬ 
spective  requirements  of  various  occasions.  A  deco¬ 
rative  scheme  in  which  light  and  medium  grays  are 
employed  produces  an  interior  which  is  very  sensitive 
to  lighting  effects.  To  these  light-and-shade  effects 
colored  light  may  add  its  charming  effectiveness.  Not 
only  are  colored  lighting  effects  able  to  add  much  to 
the  beauty  of  the  setting  but  they  possess  certain  other 
powers.  Blue  tints  produce  a  “cold”  effect  and  the 
yellow  and  orange  tints  a  “warm”  effect.  For  exam¬ 
ple,  a  room  will  appear  cooler  in  the  summer  when  illu¬ 
minated  by  means  of  bluish  light  and  a  practical  appli¬ 
cation  of  this  effect  is  in  the  theater  which  must  attract 
audiences  in  the  summer.  How  tinted  illuminants  fit 
the  spirit  of  an  occasion  or  the  mood  of  a  room  may  be 
fully  appreciated  only  through  experiments,  but  these 
are  so  effective  that  the  future  of  lighting  will  witness 
the  application  of  the  idea  of  “painting  with  light”  to 
its  fullest  extent.  Color  is  demanded  in  other  fields, 
and,  considering  its  effectiveness  and  superiority  in 
lighting,  it  will  certainly  be  demanded  in  lighting  when 
its  potentiality  becomes  appreciated  and  readily 
utilized. 

The  expressiveness  of  light  is  always  evident  in  a 
landscape.  On  a  sunny  day  the  mood  of  a  scene  varies 
throughout  the  day  and  it  grows  more  enticing  and 
agreeable  as  the  shadows  lengthen  toward  evening. 
The  artist  in  painting  a  desert  scene  employs  short 
harsh  shadows  if  he  desires  to  suggest  the  excessive 
heat.  These  shadows  suggest  the  relentless  noonday 
sun.  The  overcast  sky  is  universally  depressing  and 


314 


ARTIFICIAL  LIGHT 


it  has  been  found  that  on  a  sunny  day  most  persons  ex¬ 
perience  a  slight  depression  when  a  cloud  obscures  the 
sun.  Nature’s  lighting  varied  from  moment  to  mo¬ 
ment,  from  day  to  day,  and  from  season  to  season.  It 
presents  the  extremes  of  variation  in  distributions  of 
light  from  overcast  to  sunny  days  and  in  the  latter 
cases  the  shadows  are  continually  shifting  with  the 
sun’s  altitude.  They  are  harshest  at  noon  and  gradu¬ 
ally  fade  as  they  lengthen,  until  at  sunset  they  disap¬ 
pear.  The  colors  of  sunlit  surfaces  and  of  shadows 
vary  from  sunrise  to  sunset.  These  are  the  funda¬ 
mental  variations  in  the  lighting,  but  in  the  various 
scenes  the  lighting  effects  are  further  modified  by 
clouds  and  by  local  conditions  or  environment.  The 
vast  outdoors  provides  a  fruitful  field  for  the  study  of 
the  expressiveness  of  light. 

Having  become  convinced  of  this  power  of  light,  the 
lighting  expert  may  turn  to  artificial  light,  which  is  so 
easily  controlled  in  direction,  distribution,  and  color, 
and  draw  upon  its  potentiality.  Not  only  is  it  easy  to 
provide  a  lighting  suitable  to  the  mood  or  to  the  func¬ 
tion  of  an  interior  but  it  is  possible  to  obtain  some 
variety  in  effect  so  that  the  lighting  may  always  suit 
the  occasion.  A  study  of  nature ’s  lighting  reveals  one 
great  principle,  namely,  variety.  Mankind  demands 
variety  in  most  of  his  activities.  Work  is  varied  and 
alternated  with  recreation.  Meals  are  not  always  the 
same.  Clothing,  decorations,  and  furnishings  are  re¬ 
lieved  of  monotony.  One  of  the  most  potent  features 
of  artificial  light  is  the  ease  with  which  variety  may  be 
obtained.  In  obtaining  relief  from  the  monotony  of 
decorations  and  furnishings,  considerable  expense  and 


THE  EXPRESSIVENESS  OF  LIGHT  315 


inconvenience  are  inevitably  encountered.  With  an 
adequate  supply  of  outlets,  circuits,  and  controls  a  wide 
variety  of  lighting  effects  may  be  obtained  with  per¬ 
haps  an  insignificant  increase  in  the  initial  investment. 
Variety  is  the  spice  of  lighting  as  well  as  of  life. 

These  various  principles  of  lighting  are  readily  ex¬ 
emplified  in  the  lighting  of  the  home,  which  is  discussed 
in  another  chapter.  The  church  is  even  a  better  exam¬ 
ple  of  the  expressive  possibilities  of  lighting.  The 
architectural  features  are  generally  of  a  certain  period 
and  first  of  all  it  is  essential  to  harmonize  the  lighting 
effect  with  that  of  the  architectural  and  decorative 
scheme.  Obviously,  the  dark-stained  ceiling  of  a  cer¬ 
tain  type  of  church  would  not  be  flooded  with  light. 
The  fact  that  it  is  made  dark  by  staining  precludes  such 
a  procedure  in  lighting.  The  characteristics  of  creeds 
are  distinctly  different  and  these  are  to  some  extent 
exemplified  by  the  lines  of  the  architecture  of  their 
churches.  In  the  same  way  the  lighting  effect  may  be 
harmonized  with  the  creed  and  the  spirit  of  the  interior. 
The  lighting  may  always  be  dignified,  impressive,  and 
congruous.  Few  churches  are  properly  lighted  with  a 
high  intensity  of  illumination;  moderate  lighting  is 
more  appropriate,  for  it  is  conducive  to  the  spirit  of 
worship.  In  some  creeds  a  dominant  note  is  extreme 
penitence  and  severity.  The  architecture  may  possess 
harsh  outlines,  and  this  severity  or  extreme  solemnity 
may  be  expressed  in  lighting  by  harsher  contrasts,  al¬ 
though  this  does  not  mean  that  the  lighting  must  be 
glaring.  On  the  other  hand,  in  a  certain  modern  creed 
the  dominant  note  appears  to  be  cheerfulness.  The 
spacious  interiors  of  the  churches  of  this  creed  are 


316 


ARTIFICIAL  LIGHT 


lacking  in  severe  lines  and  the  walls  and  ceilings  are 
highly  reflecting.  Adequate  illumination  by  means  of 
diffused  light  without  the  production  of  severe  con¬ 
trasts  expresses  the  creed,  modernity,  and  enlighten¬ 
ment.  On  the  altar  of  certain  churches  the  expressive¬ 
ness  of  light  is  utilized  in  the  ceremonial  uses  which 
vary  with  the  creed.  Even  the  symbolism  of  color  may 
be  appropriately  woven  into  the  lighting  of  the  church. 

The  expressiveness  of  light  and  color  originated 
through  the  contact  of  primitive  man  with  nature. 
Sunlight  meant  warmth  and  a  bountiful  vegetation, 
but  darkness  restricted  his  activities  and  harbored 
manifold  dangers.  Many  associations  thus  originated 
and  they  were  extended  through  ignorance  and  super¬ 
stition.  Yellow  is  naturally  emblematical  of  the  sun 
and  it  became  the  symbol  of  warmth.  Brown  as  the 
predominant  color  of  the  autumn  foliage  became  tinc¬ 
tured  with  sadness  because  the  decay  of  the  vegetation 
presaged  the  death  of  the  year  and  the  cold  dreary 
months  of  winter.  The  first  signs  of  green  vegetation 
in  the  spring  were  welcomed  as  an  end  of  winter  and 
a  beginning  of  another  bountiful  summer ;  hence  green 
symbolized  youth  and  hope.  It  became  associated  with 
the  springtime  of  life  and  thus  signified  inexperience, 
but  as  the  color  of  vegetation  it  also  meant  life  itself 
and  became  a  symbol  of  immortality.  Blue  acquired 
certain  divine  attributes  because,  as  the  color  of  the 
sky,  it  was  associated  with  the  abode  of  the  gods  or 
heaven.  Also  a  blue  sky  is  the  acme  of  serenity  and 
this  color  acquired  certain  appropriate  attributes. 

Associations  of  this  character  became  woven  into 
mythology  and  thus  became  firmly  established.  Poets 


THE  EXPRESSIVENESS  OF  LIGHT  317 


have  felt  these  influences  of  light  and  color  in  nature 
and  have  given  expression  to  them  in  words.  They 
also  have  entwined  much  of  the  mythology  of  past  civil¬ 
izations  and  these  repetitions  have  helped  to  establish 
the  expressiveness  of  light  and  color.  Early  ecclesi- 
asts  employed  these  symbolisms  in  religious  ceremonies 
and  dictated  the  garbs  of  saints  and  other  religious 
personages  in  the  paintings  which  decorated  their  edi¬ 
fices.  Thus  there  were  many  influences  at  work  during 
the  early  centuries  when  intellects  were  particularly 
susceptible  through  superstition  and  lack  of  knowledge. 
The  result  has  been  an  extensive  symbolism  of  light, 
color,  and  darkness. 

At  the  present  time  it  is  difficult  to  separate  the  in¬ 
nate  appeal  of  light,  color,  and  darkness  from  those  at¬ 
tributes  which  have  been  acquired  through  associa¬ 
tions.  Possibly  light  and  color  have  no  innate  powers 
but  merely  appear  to  have  because  the  acquired  attri¬ 
butes  have  been  so  thoroughly  established  through 
usage  and  common  consent.  Space  does  not  permit  a 
discussion  of  this  point,  but  the  chief  aim  is  consum¬ 
mated  if  the  existence  of  an  expressiveness  and  im¬ 
pressiveness  of  light  is  established.  There  are  many 
other  symbolisms  of  color  and  light  which  have  arisen 
in  various  ways  but  it  is  far  beyond  the  scope  of  this 
book  to  discuss  them. 

Psychological  investigations  reveal  many  interesting 
facts  pertaining  to  the  influence  of  light  and  color  upon 
mankind.  When  choosing  color  for  color’s  sake  alone, 
that  is,  divorced  from  any  associations  of  usage,  man¬ 
kind  prefers  the  pure  colors  to  the  tints  and  shades. 
It  is  interesting  to  note  that  this  is  in  accord  with  the 


318 


ARTIFICIAL  LIGHT 


preference  exhibited  by  uncivilized  beings  in  their  use 
of  colors  for  decorating  themselves  and  their  surround¬ 
ings.  Civilized  mankind  chooses  tints  and  shades  pre¬ 
dominantly  to  live  with,  that  is,  for  the  decoration  of 
his  surroundings.  However,  civilized  man  and  the 
savage  appear  to  have  the  same  fundamental  prefer¬ 
ence  for  pure  colors  and  apparently  culture  and  refine¬ 
ment  are  responsible  for  their  difference  in  choice  of 
colors  to  live  with.  This  is  an  interesting  discovery 
and  it  has  its  applications  in  lighting,  especially  in 
spectacular  and  stage-lighting. 

It  appears  to  be  further  established  that  when  civil¬ 
ized  man  chooses  color  for  color’s  sake  alone  he  not 
only  prefers  the  pure  colors  but  among  these  he  prefers 
those  near  the  ends  of  the  spectrum,  such  as  red  and 
blue.  Red  is  favored  by  women,  with  blue  a  close  sec¬ 
ond,  but  the  reverse  is  true  for  men.  It  is  also  thor¬ 
oughly  established  that  red,  orange,  and  yellow  exert 
an  exciting  influence;  yellow-green,  green,  and  blue- 
green,  a  tranquilizing  influence,  and  blue  and  violet  a 
subduing  influence  upon  mankind.  All  these  results 
were  obtained  with  colors  divorced  from  surroundings 
and  actual  usage.  In  the  use  of  light  and  color  the 
laws  of  harmony  and  esthetics  must  be  obeyed,  but 
the  sensibility  of  the  lighting  artist  is  a  satisfactory 
guide.  Harmonies  are  of  many  varieties,  but  they  may 
be  generally  grouped  into  two  classes,  those  of  analogy 
and  those  of  contrast.  The  former  includes  colors 
closely  associated  in  hue  and  the  latter  includes  comple¬ 
mentary  colors.  No  rules  in  simplified  form  can  be 
presented  for  the  production  of  harmonies  in  light  and 
color.  These  simplifications  are  made  only  by  those 


THE  EXPRESSIVENESS  OF  LIGHT  319 


who  have  not  looked  deeply  enough  into  the  subject 
through  observation  and  experiment  to  see  its  com¬ 
plexity. 

The  expressiveness  of  light  finds  applications 
throughout  the  vast  field  of  lighting,  but  the  stage 
offers  great  opportunities  which  have  been  barely 
drawn  upon.  When  one  has  awakened  to  the  vast  pos¬ 
sibilities  of  light,  shade,  and  color  as  a  means  of  ex¬ 
pression  it  is  difficult  to  suppress  a  critical  attitude 
toward  the  crudity  of  lighting  effects  on  the  present 
stage,  the  lack  of  knowledge  pertaining  to  the  latent 
possibilities  of  light,  and  the  superficial  use  of  this 
potential  medium.  The  crude  realism  and  the  almost 
total  absence  of  deep  insight  into  the  attributes  of 
light  and  color  are  the  chief  defects  of  stage-lighting 
to-day.  One  turns  hopefully  toward  the  gallant  though 
small  band  of  stage  artists  who  are  striving  to  realize 
a  harmony  of  lighting,  setting,  and  drama  in  the  so- 
called  modern  theater.  Unappreciated  by  a  public 
which  flocks  to  the  melodramatic  movie,  whose  scenar¬ 
ios  produced  upon  the  legitimate  stage  would  be  jeered 
by  the  same  public,  the  modern  stage  artist  is  striving 
to  utilize  the  potentiality  of  light.  But  even  among 
these  there  are  impostors  who  have  never  achieved 
anything  worth  while  and  have  not  the  perseverance  to 
learn  to  extract  some  of  the  power  of  light  and  to  apply 
it  effectively.  Lighting  suffers  in  the  hands  of  the 
artist  owing  to  the  absence  of  scientific  knowledge  and 
it  is  misused  by  the  engineer  who  does  not  possess  an 
esthetic  sensibility.  Science  and  art  must  be  linked  in 
lighting. 

The  worthy  efforts  of  stage  artists  in  some  of  the 


320 


ARTIFICIAL  LIGHT 


modern  theaters  lack  the  support  of  the  producers,  who 
cater  to  the  taste  of  the  public  which  pays  the  admis¬ 
sion  fees.  Apparently  the  modern  theater  must  first 
pass  through  a  period  in  which  financial  support  must 
be  obtained  from  those  who  are  able  to  give  it,  just  as 
the  symphony  orchestra  has  been  supported  for  the 
sake  of  art.  Certainly  the  time  is  at  hand  for  philan¬ 
thropy  to  come  to  the  aid  of  worthy  and  capable  stage 
artists  who  hope  to  rescue  theatrical  production  from 
the  mire  of  commercialism. 

Those  who  have  not  viewed  stage-lighting  from  be¬ 
hind  the  scenes  would  often  be  surprised  at  the  crudity 
of  the  equipment,  and  especially  at  the  superficial  in¬ 
tellects  which  are  responsible  for  some  of  the  realistic 
effects  obtained.  But  these  are  the  result  usually  of 
experiment,  not  of  directed  knowledge.  Furthermore, 
little  thought  is  given  to  the  emotional  value  of  light, 
shade,  and  color.  The  flood  of  light  and  the  spot  of 
light  are  varied  with  gaudy  color-effects,  but  how  sel¬ 
dom  is  it  possible  to  distinguish  a  deep  relation  between 
the  lighting  and  the  dramatic  incidents ! 

In  much  of  the  foregoing  discussion  the  present  pre¬ 
dominating  theatrical  productions  are  not  considered, 
for  the  lighting  effects  are  good  enough  for  them. 
Many  ingenious  tricks  and  devices  are  resorted  to  in 
these  productions,  and  as  a  whole  lighting  is  serving 
effectively  enough.  But  in  considering  the  expressive¬ 
ness  of  light  the  deeper  play  is  the  medium  necessary 
for  utilizing  the  potentiality  of  light.  These  are  rare 
and  unfortunately  the  stage  artist  appreciative  of  the 
significations  and  emotional  value  of  light  and  color  is 
still  rarer. 


Soldiers’  and  Sailors’  Monument 


Jeweled  portal  welcoming  returned  soldiers 


ARTIFICIAL  LIGHT  HONORING  THOSE  WHO  FELL  AND  THOSE  WHO 

RETURNED 


THE  EXPRESSIVENESS  OF  LIGHT  IN  CHURCHES 


THE  EXPRESSIVENESS  OF  LIGHT  321 

The  equipment  of  the  present  stage  consists  of  foot¬ 
lights,  side-lights,  border-lights,  flood-lights,  spot¬ 
lights,  and  much  special  apparatus.  One  of  the  sever¬ 
est  criticisms  of  stage-lighting  from  an  artistic  point 
of  view  may  be  directed  against  the  use  of  footlights 
for  obtaining  the  dominant  light.  This  is  directed  up¬ 
ward  and  the  effect  is  an  unnatural  and  even  a  gro¬ 
tesque  modeling  of  the  actors’  features.  The  shadows 
produced  are  incongruous,  for  they  are  opposed  to  the 
other  real  and  painted  effects  of  light  and  shade.  The 
only  excuse  for  such  lighting  is  that  it  is  easily  done 
and  that  proper  lighting  is  difficult  to  obtain,  owing  to 
the  fact  that  it  involves  a  change  in  construction.  By 
no  means  should  the  footlights  be  abandoned,  for  they 
would  still  be  invaluable  in  obtaining  diffused  light 
even  when  the  dominant  light  is  directed  from  above 
the  horizontal.  In  the  present  stage-lighting,  in  which 
the  footlights  generally  predominate,  the  expressive¬ 
ness  of  light  is  not  satisfactory.  Perhaps  they  are  a 
necessary  compromise,  but  inasmuch  as  their  effect  is 
unnatural  they  should  not  be  accepted  until  it  is  thor¬ 
oughly  proved  that  ingenuity  cannot  eliminate  the 
present  defects. 

The  stage  as  a  whole  is  a  mobile  picture  in  light, 
shade,  and  color  with  the  addition  of  words  and  music. 
Excepting  the  latter,  it  is  an  expression  of  light  worthy 
of  the  same  care  and  consideration  that  the  painting, 
which  is  also  an  expression  of  light,  receives  from  the 
artist.  The  scenery  and  costumes  should  be  considered 
in  terms  of  the  lighting  effects  because  they  are  affected 
by  changes  in  the  color  of  the  light.  In  fact,  the  author 
showed  a  number  of  years  ago  that  by  carefully  relat- 


322 


ARTIFICIAL  LIGHT 


ing  the  colors  of  the  light  with  the  colors  used  in  paint¬ 
ing  the  scenery,  a  complete  change  of  scene  can  be  ob¬ 
tained  by  merely  changing  the  color  of  the  light. 
Rather  wonderful  dissolving  effects  can  be  produced 
in  this  manner  without  shifting  scenery.  For  example, 
a  warm  summer  scene  with  trees  in  full  foliage  under 
a  yellow  light  may  be  changed  under  a  bluish  light  to  a 
winter  scene  with  ground  covered  with  snow  and  trees 
barren  of  leaves.  But  before  such  accomplishments 
can  be  realized  upon  the  stage,  scientific  knowledge 
must  be  available  behind  the  scenes. 

The  art  museum  affords  a  multitude  of  opportuni¬ 
ties  for  utilizing  the  expressiveness  of  light.  This  is 
more  generally  true  of  sculptured  objects  than  of  paint¬ 
ings  because  the  latter  may  be  treated  as  a  whole.  The 
artist  almost  invariably  paints  a  picture  by  daylight 
and  unless  it  is  illuminated  by  daylight  it  is  altered  in 
appearance,  that  is,  it  becomes  another  picture.  The 
great  difference  in  the  appearance  of  a  painting  under 
daylight  and  ordinary  artificial  light  is  quite  startling, 
when  demonstrated  by  means  of  apparatus  in  which 
the  two  effects  may  be  rapidly  alternated.  Art  mu¬ 
seums  are  supposed  to  exhibit  the  works  of  artists  and, 
therefore,  no  changes  in  these  works  should  be  tolerated 
if  they  can  be  avoided.  The  modern  artificial-daylight 
lamps  make  it  possible  to  illuminate  galleries  with 
light  at  night  which  approximates  daylight.  A  further 
advantage  of  artificial  light  is  that  it  may  be  easily  con¬ 
trolled  and  a  more  satisfactory  lighting  may  be  ob¬ 
tained  than  with  natural  light.  Considering  the  cost  of 
daylight  in  museums  and  its  disadvantages  it  appears 
possible  that  artificial  daylight  with  its  advantages 


THE  EXPRESSIVENESS  OF  LIGHT  323 


may  replace  it  eventually  in  the  large  galleries.  If 
the  works  of  artists  are  really  prized  for  their  appear¬ 
ance,  the  lighting  of  them  is  very  important. 

Sculpture  is  modeled  by  light  and  although  it  is 
impossible  to  ascertain  the  lighting  under  which  the 
sculptor  viewed  his  completed  work  with  pride  and 
satisfaction,  it  is  possible  to  give  the  best  considera¬ 
tion  to  its  lighting  in  its  final  place  of  exhibition.  The 
appearance  of  a  sculpture  depends  upon  the  dominant 
direction  of  the  light,  the  solid-angle  subtended  by  the 
light-source  ( skylight,  area  of  sky,  etc. )  and  the  amount 
of  scattered  light.  The  direction  of  dominant  light 
determines  the  general  direction  of  the  shadows;  the 
solid-angle  of  the  light-source  affects  the  character  of 
the  edges  of  the  shadows  ;  and  the  scattered  light  ac¬ 
counts  for  the  brightness  of  the  shadows.  It  should 
be  obvious  that  variations  of  these  factors  affect  the  ap¬ 
pearance  or  expression  of  three-dimensional  objects. 
Therefore  the  position  of  a  sculptured  object  with  re¬ 
spect  to  the  window  or  other  skylight  and  the  amount 
of  light  reflected  from  the  surroundings  are  important. 
Visits  to  art  museums  with  these  factors  in  mind  re¬ 
veal  a  gross  neglect  in  the  lighting  of  objects  of  art 
which  are  supposed  to  appeal  by  virtue  of  their  ap¬ 
pearances,  for  they  can  arouse  the  emotions  only 
through  the  doorway  of  vision. 

A  century  ago  mankind  gave  no  thought  to  utilizing 
the  expressive  and  impressive  powers  of  light  except 
in  religious  ceremonies.  It  was  not  practicable  to 
utilize  light  from  the  feeble  flames  of  those  days  in  the 
elaborate  manner  necessary  to  draw  upon  these  powers. 
Man  was  concerned  with  the  more  pressing  needs.  He 


324 


ARTIFICIAL  LIGHT 


wanted  enough  light  to  make  the  winter  evenings  en¬ 
durable  and  the  streets  reasonably  safe.  The  artists 
of  those  days  saw  the  wonderful  expressions  of  light 
exhibited  by  Nature,  but  they  dared  not  dream  of  rival¬ 
ing  these  with  artificial  light.  To-day  Nature  sur¬ 
passes  man  in  the  production  of  lighting  effects  only  in 
magnitude.  Man  surpasses  her  artistically.  In  fact, 
the  artist  becomes  a  master  only  when  he  can  improve 
upon  her  settings ;  when  he  is  able  by  rare  judgment  in 
choosing  and  in  eliminating  and  by  skill  and  ingenuity 
to  substitute  a  complete  harmony  for  her  incomplete 
and  unsatisfactory  reality.  But  everywhere  Nature  is 
the  great  teacher,  for  her  world  is  full  of  an  everchang- 
ing  infinitude  of  expressions  of  light.  Mankind  needs 
only  to  study  these  with  an  attuned  sensibility  to  be 
able  eventually  to  play  the  music  of  light  for  those  who 
are  blessed  with  an  esthetic  sense. 


XXIV 

LIGHTING  THE  HOME 


In  the  home  artificial  light  exerts  its  influence  upon 
every  one.  Without  artificial  lighting  the  family  cir¬ 
cle  may  not  have  become  the  important  civilizing  in¬ 
fluence  that  it  is  to-day.  Certainly  civilized  man  now 
shudders  at  the  thought  of  spending  his  evenings  in 
the  light  of  the  fire  upon  the  hearth  or  of  a  burning 
splinter. 

The  importance  of  artificial  light  is  emphatically  im¬ 
pressed  upon  the  householder  when  he  is  forced  tem¬ 
porarily  to  depend  upon  the  primitive  candle  through 
the  failure  of  the  modern  system  of  lighting.  He  flees 
from  his  home  to  that  of  his  more  fortunate  neighbor, 
or  he  retires  in  his  helplessness  to  awaken  in  the  morn¬ 
ing  with  a  blessing  for  daylight.  He  cannot  conceive 
of  happiness  and  recreation  in  the  homes  of  a  century 
or  two  ago,  when  a  few  candles  or  an  oil-lamp  or  two 
were  the  sole  sources  of  light.  But  when  the  electric 
or  gas  service  is  again  restored  he  relapses  shortly  into 
his  former  placid  indifference  toward  the  wonderfully 
efficient  and  adequate  artificial  light  of  the  present  age. 

Until  recently  artificial  light  was  costly  and  the 
householder  in  common  with  other  users  of  light  did 
not  concern  himself  with  the  question  of  adequate  and 
artistic  lighting.  His  chief  aim  was  to  utilize  as  little 
as  possible,  for  cost  was  always  foremost  in  his  mind. 

325 


326 


ARTIFICIAL  LIGHT 


The  development  of  the  science  of  light-production  has 
been  so  rapid  during  the  past  generation  that  adequate, 
efficient,  and  cheap  artificial  light  finds  mankind  un¬ 
consciously  viewing  lighting  with  the  same  attitude  as 
he  displays  toward  his  food  and  fuel  bills.  Another 
consequence  of  this  rapid  development  is  that  mankind 
does  not  know  how  to  extract  the  joy  from  modern  arti¬ 
ficial  light.  This  is  readily  demonstrated  by  analyzing 
the  lighting  of  middle-class  homes. 

The  cost  of  light  has  been  discussed  in  another  chap¬ 
ter  and  it  has  been  shown  that  it  has  decreased  enor¬ 
mously  in  a  century.  It  is  now  the  most  potential 
agency  in  the  home  when  viewed  from  the  standpoint 
of  cost.  The  average  householder  pays  less  than 
twenty  dollars  per  year  for  ever-ready  light  through¬ 
out  his  home.  For  about  five  cents  per  day  the  aver¬ 
age  family  enjoys  all  the  blessings  of  modern  lighting, 
which  is  sufficient  proof  that  cost  is  an  insignificant 
item. 

In  order  to  simplify  the  discussion  of  lighting  the 
home  the  terminology  of  electric-lighting  will  be  used. 
The  principles  expounded  apply  as  well  to  gas  as  to 
electricity,  and  owing  to  the  ingenuity  of  the  gas¬ 
lighting  experts,  the  possibilities  of  gas-lighting  are 
extensive  despite  its  handicaps.  There  are  some  places 
in  the  home,  such  as  the  kitchen  and  basement,  where 
lighting  is  purely  utilitarian  in  the  narrow  sense,  but 
in  most  of  the  rooms  the  esthetic  or,  more  broadly,  the 
psychological  aspects  of  lighting  should  dominate. 
Pure  utility  is  always  a  by-product  of  artistic  lighting 
and  furthermore,  the  lighting  effects  will  be  without 
glare  when  they  satisfy  all  the  demands  of  esthetics. 


LIGHTING  THE  HOME 


327 


In  dealing  with  lighting  in  the  home  the  householder 
should  concentrate  his  attention  upon  lighting  effects. 
Unfortunately,  he  is  not  taught  to  do  so,  for  every¬ 
where  he  turns  for  help  he  finds  the  discussion  directed 
toward  fixtures  and  lamps  instead  of  toward  lighting 
effects.  However,  these  are  merely  links  in  the  chain 
from  the  meter  to  the  eye.  Lamps  are  of  interest  from 
the  standpoint  of  quantity  and  quality  of  light,  and  fix¬ 
tures  are  of  importance  chiefly  as  distributers  of  light. 
These  details  are  merely  means  to  an  end  and  the  end 
is  the  lighting  effect.  Of  course,  the  fixtures  are  more 
important  as  objects  than  the  wires  because  they  are 
visible  and  should  harmonize  with  the  general  decora¬ 
tive  and  architectural  scheme. 

The  home  is  the  theater  of  life  full  of  various  moods 
and  occasions ;  hence  the  lighting  of  a  home  should  be 
flexible.  A  degree  of  variety  should  be  possible.  Con¬ 
trols,  wiring,  outlets,  and  fixtures  should  conspire  to 
provide  this  variety.  At  the  present  time  the  average 
householder  does  not  give  much  attention  to  lighting 
until  he  purchases  fixtures.  It  is  probable  that  he 
thought  of  it  when  he  laid  out  or  approved  the  wiring, 
but  usually  he  does  not  consider  it  seriously  until  he 
visits  the  fixture-dealer  to  purchase  fixtures.  And 
then  unfortunately  the  fixture-dealer  does  not  light  his 
home ;  he  does  not  sell  the  householder  lighting-effects 
designed  to  meet  the  requirements  of  the  particular 
home ;  he  sells  merely  fixtures. 

Unfortunately  there  are  few  fixtures  available  which 
have  definite  aims  in  lighting  as  demanded  by  the  home. 
Of  the  great  variety  of  fixtures  available  there  are 
many  artistic  objects,  but  it  is  obvious  that  little  at- 


328 


ARTIFICIAL  LIGHT 


tention  is  given  to  their  design  from  the  standpoint  of 
lighting.  That  the  fixture-dealer  usually  thinks  of 
fixtures  as  objects  and  gives  little  or  no  thought  to 
lighting  effects  is  apparent  from  his  conversation  and 
from  his  display.  He  exhibits  fixtures  usually  en 
masse  and  seldom  attempts  to  illustrate  the  lighting 
effects  produced  in  the  room. 

The  foregoing  criticisms  are  presented  to  emphasize 
the  fact  that  throughout  the  field  of  lighting  the  great 
possibilities  which  have  been  opened  by  modern  light- 
sources  are  not  fully  appreciated.  The  point  at  which 
to  begin  to  design  the  lighting  for  a  home  is  the  wiring. 
Unfortunately  this  is  too  often  done  by  a  contractor 
who  has  given  no  special  thought  to  the  possibilities 
of  lighting  and  to  the  requirements  in  wiring  and 
switches  necessary  in  order  to  realize  them.  At  this 
point  the  householder  should  attempt  to  form  an  opin¬ 
ion  as  to  the  relative  values.  Is  artificial  lighting  im¬ 
portant  enough  to  warrant  an  expenditure  of  two  per 
cent,  of  the  total  investment  in  the  home  and  its  fur¬ 
nishings?  The  answer  will  depend  upon  the  extent  to 
which  artificial  light  is  appreciated.  It  appears  that 
four  or  five  per  cent,  is  not  too  much  if  it  is  admitted 
that  the  artificial  lighting  system  ranks  next  to  the 
heating  plant  in  importance  and  that  these  two  are  the 
most  important  features  of  an  interior  of  a  residence. 
A  switch  or  a  baseboard  outlet  costs  an  insignificant 
sum  but  either  may  pay  for  itself  many  times  in  the 
course  of  a  few  years  through  its  utility  or  convenience. 

It  appears  best  to  take  up  this  subject  room  by  room 
because  the  requirements  vary  considerably,  but  in 
order  to  be  specific  in  the  discussions,  a  middle-class 


LIGHTING  THE  HOME 


329 


home  will  be  chosen.  The  more  important  rooms  will 
be  treated  first  and  various  simple  details  will  be 
touched  upon  because,  after  all,  the  proper  lighting  of 
a  home  is  realized  by  attention  to  small  details. 

The  living-room  is  the  scene  of  many  functions.  It 
serves  at  times  for  the  quiet  gathering  of  the  family, 
each  member  devoted  to  reading.  At  another  time  it 
may  contain  a  happy  company  engaged  at  cards  or  in 
conversation.  The  lighting  requirements  vary  from  a 
spot  or  two  of  light  to  a  flood  of  light.  Excepting  in 
the  small  living-rooms  there  does  not  appear  to  be  a 
single  good  reason  for  a  ceiling  fixture.  It  is  nearly 
always  in  the  field  of  vision  when  occupants  are  en¬ 
gaged  in  conversation,  and  for  reading  purposes  the 
portable  lamp  of  satisfactory  design  has  no  rival. 
Wall  brackets  cannot  supply  general  lighting  without 
being  too  bright  for  comfort.  If  they  are  heavily 
shaded  they  may  still  emit  plenty  of  light  upward,  but 
the  adjacent  spots  on  the  walls  or  ceiling  will  generally 
be  too  bright.  Wall  brackets  may  be  beautiful  orna¬ 
ments  and  decorative  spots  of  light  and  have  a  right 
to  exist  as  such,  but  they  cannot  be  safely  depended 
upon  for  adequate  general  lighting  on  those  occasions 
which  demand  such  lighting. 

As  a  general  principle,  it  is  well  to  visualize  the  fur¬ 
niture  in  the  room  when  looking  at  the  architect’s  draw¬ 
ings  and  it  is  advantageous  even  to  cut  out  pieces  of 
paper  representing  the  furniture  in  scale.  By  placing 
these  on  the  drawings  the  furnished  room  is  readily 
visualized  and  the  locations  of  baseboard  outlets  be¬ 
come  evident.  It  appears  that  the  best  method  of 
lighting  a  living-room  is  by  means  of  decorative  port- 


330 


ARTIFICIAL  LIGHT 


able  lamps.  Such  lamps  are  really  lighting-furniture, 
for  they  aid  in  decorating  and  in  furnishing  the  room 
at  all  times.  A  number  of  these  lamps  in  the  living- 
room  insures  great  flexibility  in  the  lighting,  and  the 
light  may  be  kept  localized  if  desired  so  that  the  room 
is  restful.  A  room  whose  ceiling  and  walls  are  bril¬ 
liantly  illuminated  is  not  so  comfortable  for  long  peri¬ 
ods  as  one  in  which  these  areas  are  dimly  lighted. 
Furthermore,  the  latter  is  more  conducive  to  reading 
and  to  other  efforts  at  concentration.  The  furniture 
may  be  readily  shifted  as  desired  and  the  portable 
lamps  may  be  rearranged. 

Such  lighting  serves  all  the  purposes  of  the  living- 
room  excepting  those  requiring  a  flood  of  light,  but  it 
is  easy  to  conceal  elaborate  lighting  mechanisms  under¬ 
neath  the  shades  of  portable  lamps.  Several  types  of 
portable  lamps  are  available  which  supply  an  indirect 
component  as  well  as  direct  light.  The  former  illumi¬ 
nates  the  ceiling  with  a  flood  of  light  without  any  dis¬ 
comforting  glare.  Such  a  lighting-unit  is  one  of  the 
most  satisfactory  for  the  home,  for  two  distinct  effects 
and  a  combination  of  these  introduce  a  desirable  ele¬ 
ment  of  variety  into  the  lighting.  Not  less  than  four 
and  preferably  six  baseboard  outlets  should  be  pro¬ 
vided  in  a  living-room  of  moderate  size.  One  outlet 
on  the  mantel  is  also  to  be  desired  for  connecting 
decorative  candlesticks,  and  brackets  above  the  fire¬ 
place  are  of  ornamental  value.  Although  the  absence 
of  ceiling  fixtures  improves  the  appearance  of  the  room, 
wiring  may  be  provided  for  ceiling  outlets  in  new 
houses  as  a  matter  of  insurance  against  the  possible 
needs  of  the  future.  When  ceiling  fixtures  are  not 


LIGHTING  THE  HOME 


331 


used,  switches  may  be  provided  for  the  mantel  brack¬ 
ets  or  certain  baseboard  outlets  in  order  that  light  may 
be  had  upon  entering  the  room. 

The  merits  of  a  portable  lamp  may  be  ascertained 
before  purchasing  by  actual  demonstration.  Some  of 
them  are  not  satisfactory  for  reading-lamps,  owing  to 
the  shape  of  the  shade  or  to  the  position  of  the  lamps. 
The  utility  of  a  table  lamp  may  be  determined  by  plac¬ 
ing  it  upon  a  table  and  noting  the  spread  of  light  while 
seated  in  a  chair  beside  it.  A  floor  lamp  may  also  be 
tested  very  easily.  A  miniature  floor  lamp  about 
four  feet  in  height  with  an  appropriate  shade  provides 
an  excellent  lamp  for  reading  purposes  because  it  may 
be  placed  by  the  side  of  a  chair  or  moved  about  inde¬ 
pendent  of  other  furniture.  A  tall  floor  lamp  often 
serves  for  lighting  the  piano,  but  small  piano  lamps 
may  be  found  which  are  decorative  as  well  as  service¬ 
able  in  illuminating  the  music  without  glare. 

The  dining-room  presents  an  entirely  different  prob¬ 
lem  for  the  setting  is  very  definite.  The  dining-table 
is  the  most  important  area  in  the  room  and  it  should  be 
the  most  brilliantly  illuminated  area  in  the  room.  A 
demonstration  of  this  point  is  thoroughly  convincing. 
The  decorator  who  designs  wall  brackets  for  the  dining¬ 
room  is  interested  in  beautiful  objects  of  art  and  not  in 
a  proper  lighting  effect.  The  fixture-dealer,  having 
fixtures  to  sell  and  not  recognizing  that  he  could  fill  a 
crying  need  as  a  lighting  specialist,  is  as  likely  to  sell 
a  semi-indirect  or  an  indirect  lighting  fixture  as  he  is 
to  provide  a  properly  balanced  lighting  effect  with  the 
table  brightly  illuminated.  The  indirect  and  semi-indi¬ 
rect  units  illuminate  the  ceiling  predominantly  with 


332 


ARTIFICIAL  LIGHT 


the  result  that  this  bright  area  distracts  attention 
from  the  table.  A  brightly  illuminated  table  holds  the 
attention  of  the  diners.  Light  attracts  and  a  semi¬ 
darkness  over  the  remainder  of  the  room  crowds  in 
with  a  result  that  is  far  more  satisfactory  than  that  of 
a  dining-room  flooded  with  light. 

The  old-fashioned  dome  which  hung  over  the  dining- 
table  has  served  well,  for  it  illuminated  the  table  and 
left  the  remainder  of  the  room  dimly  lighted.  But  its 
wide  aperture  made  it  necessary  to  suspend  it  rather 
low  in  order  that  the  lamps  within  should  not  be 
visible.  It  is  an  obtrusive  fixture  and  despite  its  ex¬ 
cellent  lighting  effect,  it  went  out  of  style.  But  satis¬ 
factory  lighting  principles  never  become  antiquated, 
and  as  taste  in  fixtures  changes  the  principles  may  be 
retained  in  new  fixtures.  Modern  domes  are  available 
which  are  excellent  for  the  dining-room  if  the  lamps  are 
well  concealed.  The  so-called  showers  are  satisfactory 
if  the  shades  are  dense  and  of  such  shape  as  to  conceal 
the  lamps  from  the  eyes.  Various  modifications  read¬ 
ily  suggest  themselves  to  the  alert  fixture-designer. 
Even  the  housewife  can  do  much  with  silk  shades  when 
the  principle  of  lighting  the  dining-table  is  understood. 
The  so-called  cadelabra  have  been  sold  extensively  for 
dining-rooms  and  they  are  fairly  satisfactory  if 
equipped  with  shades  which  reflect  much  of  the  light 
downward.  Semi-indirect  and  indirect  fixtures  have 
many  applications  in  lighting,  but  they  do  not  provide 
the  proper  effect  for  a  dining-room. 

It  is  easy  to  make  a  special  fixture  which  will  send  a 
component  of  light  downward  to  the  table  and  will  per¬ 
mit  a  small  amount  of  diffused  light  to  the  ceiling  and 


LIGHTING  THE  HOME 


333 


walls.  If  a  daylight  lamp  is  used  for  the  direct  com¬ 
ponent,  the  table  will  appear  very  beantifnl.  Under 
this  light  the  linen  and  china  are  white,  flowers  and 
decorations  on  the  china  appear  in  their  full  colors,  the 
silver  is  attractive,  and  the  various  color-harmonies 
such  as  butter,  paprika,  and  baked  potato  are  enticing. 
This  is  an  excellent  place  for  a  daylight  lamp  if  dif¬ 
fused  light  illuminating  the  remainder  of  the  room  and 
the  faces  of  the  diners  is  of  a  warm  tone  obtained  by 
warm  yellow  lamps  or  by  filtering  these  components  of 
the  light  through  orange  shades.  The  ceiling  fixture 
should  be  provided  with  two  circuits  and  switches.  In 
some  cases  it  is  easy  to  provide  a  dangling  plug  for 
connecting  such  electric  equipment  as  a  toaster,  perco¬ 
lator,  or  candlesticks.  Two  candlesticks  are  effective 
on  the  buffet,  but  usually  the  smallest  normal-voltage 
lamps  available  give  too  much  light.  Miniature  lamps 
may  be  used  with  a  small  transformer,  or  two  regular 
lamps  may  be  connected  in  series.  At  least  two  base¬ 
board  outlets  are  convenient. 

The  foregoing  deals  with  the  more  or  less  essential 
lighting  of  a  dining-room,  but  there  are  various  prac¬ 
ticable  additional  lighting  effects  which  add  much 
charm  to  certain  occasions.  Colored  light  of  low  in¬ 
tensity  obtained  from  a  cove  or  from  “flower-boxes” 
fastened  upon  the  wall  is  very  pleasing.  If  a  cove  is 
provided  around  the  room,  two  circuits  containing 
orange  and  blue  lamps  respectively  will  supply  two 
colors  widely  differing  in  effect.  By  mixing  the  two  a 
beautiful  rose  tint  may  be  obtained.  This  equipment 
has  been  installed  with  much  satisfaction.  A  simpler 
method  of  obtaining  a  similar  effect  is  to  use  imitation 


334 


ARTIFICIAL  LIGHT 


flower-boxes  plugged  into  wall  outlets.  Artificial  foli¬ 
age  adds  to  the  charm  of  these  boxes.  The  colored 
light  is  merely  to  add  another  effect  on  special  occa¬ 
sions  and  its  intensity  should  never  be  high.  In  the 
dining-room  such  unusual  effects  are  not  out  of  place 
and  they  need  not  be  garish. 

The  sun-room  partakes  of  the  characteristics  of  the 
living-room  to  some  extent,  but,  it  being  smaller,  a 
semi-indirect  fixture  may  be  satisfactory  for  general 
illumination.  However,  a  portable  lamp  which  sup¬ 
plies  an  indirect  component  of  light  besides  the  direct 
light  serves  admirably  for  reading  as  well  as  for  flood¬ 
ing  the  room  with  light  when  necessary.  Two  or  three 
baseboard  outlets  are  desirable  for  attaching  decora¬ 
tive  or  even  purely  utilitarian  lamps.  The  sun-room 
is  an  excellent  place  for  utilizing  “flower-box”  fix¬ 
tures  decorated  with  artificial  foliage.  In  fact,  a  cen¬ 
tral  fixture  may  assume  the  appearance  of  a  “  hanging 
basket’ ’  of  foliage.  The  library  and  den  offer  no  prob¬ 
lems  differing  from  those  already  discussed  in  the 
living-room.  A  careful  consideration  of  the  disposi¬ 
tion  of  the  furniture  will  reveal  the  best  positions  for 
the  outlets.  In  a  small  library  wall  brackets  may  serve 
as  decorative  spots  of  light  and  if  the  shades  are  pen¬ 
dent  they  may  serve  as  lamps  for  reading  purposes. 
In  both  these  rooms  an  excellent  reading-lamp  is  de¬ 
sired,  but  it  may  be  decorative  as  well.  Wall  outlets 
may  be  desired  for  decorative  portable  lamps  upon  the 
bookcases. 

The  sleeping-room,  which  commonly  is  also  a  dress¬ 
ing-room,  often  exhibits  the  errors  of  a  lack  of  fore¬ 
sight  in  lighting.  In  most  rooms  of  this  character 


LIGHTING  THE  HOME 


335 

there  is  one  best  arrangement  of  furniture  and  if  this 
is  determined  it  is  easy  to  ascertain  where  the  windows 
and  outlets  should  be  located.  The  windows  may  usu¬ 
ally  be  arranged  for  twin  beds  as  well  as  for  a  single 
one  with  obvious  advantages  of  flexibility  in  arrange¬ 
ment.  With  the  position  of  the  bureau  determined  it 
is  easy  to  locate  outlets  for  two  wall  brackets,  one  on 
each  side,  about  sixty-six  inches  above  the  floor  and 
about  five  feet  apart.  When  the  brackets  are  equipped 
with  dense  upright  shades,  the  figure  before  the  mirror 
is  well  illuminated  without  glare  and  sufficient  light 
reaches  the  ceiling  to  illuminate  the  whole  room. 

A  baseboard  outlet  should  be  available  for  small 
portable  lamps  which  may  be  used  upon  the  bureau  or 
for  electric  heating  devices.  The  same  is  true  for  the 
dressing-table;  indeed,  two  small  decorative  lamps  on 
the  table  serve  better  than  high  wall  brackets  owing  to 
the  fact  that  the  user  is  seated.  A  baseboard  outlet 
near  the  head  of  the  bed  or  between  the  beds  is  con¬ 
venient  for  a  reading-lamp  and  for  other  purposes. 
An  outlet  in  the  center  of  the  ceiling  controlled  by  a 
convenient  switch  may  be  installed  on  building,  as  in¬ 
surance  against  future  needs  or  desires.  But  a  single 
lighting-unit  in  the  center  of  the  ceiling  does  not  serve 
adequately  the  needs  at  the  bureau  and  dressing-table. 
In  fact,  two  wall  brackets  properly  located  with  respect 
to  the  bureau  afford  a  lighting  much  superior  for  all 
purposes  in  the  bedroom  to  that  produced  by  a  ceiling 
fixture. 

In  the  bath-room  the  principal  problem  is  to  illu¬ 
minate  the  person,  especially  the  face,  before  the  mir¬ 
ror.  Many  mistakes  are  made  at  this  point,  despite  the 


336 


ARTIFICIAL  LIGHT 


simplicity  of  the  solution.  In  order  to  see  the  image 
of  an  object  in  a  mirror,  the  object  must  be  illuminated. 
It  is  best  to  do  this  in  a  straightforward  manner  by 
means  of  a  small  lighting-unit  on  each  side  of  the  mir¬ 
ror  at  a  height  of  five  feet.  Both  sides  of  the  face  will 
be  well  illuminated  and  the  liglit-sources  are  low 
enough  to  eliminate  objectionable  shadows.  The  units 
may  be  merely  pull-chain  sockets  containing  frosted 
or  opal  lamps.  A  center  bracket  or  a  single  unit  sus¬ 
pended  from  the  ceiling  is  not  as  satisfactory  as  the 
two  brackets.  These  afford  enough  light  for  the  entire 
bath-room.  A  baseboard  or  wall  outlet  is  convenient 
for  connecting  a  heater,  curling-iron,  and  other  elec¬ 
trically  heated  devices. 

The  sewing-room,  which  in  the  middle-class  home  is 
usually  a  small  room,  is  sometimes  used  as  a  bedroom. 
A  ceiling  fixture  will  supply  adequate  general  light¬ 
ing,  but  a  baseboard  outlet  should  be  available  for  a 
short  floor  lamp  or  a  table  lamp  for  sewing  purposes. 
An  intense  local  light  is  necessary  for  this  occupation, 
which  severely  taxes  the  eyes.  A  so-called  daylight 
lamp  serves  very  well  in  this  case. 

In  the  kitchen  the  wall  brackets  are  easily  located 
after  the  positions  of  the  range,  work-table,  sink,  etc., 
are  determined.  A  bracket  for  each  is  advisable  un¬ 
less  they  are  so  located  that  one  will  serve  two  pur- 
looses.  It  is  customary  to  have  a  combination  fixture 
for  gas  and  electricity.  This  is  often  suspended  from 
the  center  of  the  ceiling,  but  inasmuch  as  the  gas-light 
cannot  be  close  to  the  ceiling,  the  fixture  extends  so 
far  downward  as  to  become  a  nuisance.  Further¬ 
more,  a  liglit-source  hung  low  from  the  center  of  the 


OBTAINING  TWO  DIFFERENT  MOODS  IN  A  ROOM  BY  A  PORTABLE  LAMP 
WHICH  SUPPLIES  DIRECT  AND  INDIRECT  COMPONENTS  OF  LIGHT 


THE  LIGHTS  OP  NEW  YORK  CITY 

Towering  shafts  of  light  defy  the  darkness  and  thousands  of  lighted  windows  symbolize  man’s  successful  struggle  against  nature 


LIGHTING  THE  HOME 


337 


ceiling  is  in  such  a  position  that  the  worker  in  the 
kitchen  usually  works  in  his  shadow.  If  a  ceiling  out¬ 
let  is  used  it  should  be  an  electrical  socket  at  the  ceil¬ 
ing.  The  combination  fixture  is  best  placed  on  the 
wall  as  a  bracket.  The  so-called  daylight  lamps  are 
valuable  in  the  kitchen. 

In  the  basement  a  generous  supply  of  ceiling  outlets 
adds  much  to  the  satisfaction  of  a  basement.  One  in 
each  locker,  one  before  the  furnace,  and  a  large  day¬ 
light  lamp  above  but  to  one  side  of  the  laundry  trays 
are  worth  many  times  their  cost.  Furthermore,  a  wall 
socket  for  the  electric  iron  and  washing-machine  is  a 
convenience  very  much  appreciated. 

In  the  stairways  convenient  three-way  switches  for 
each  of  the  ceiling  fixtures  represents  the  best  practice. 
A  baseboard  outlet  in  the  upper  hall  affords  a  connec¬ 
tion  for  a  decorative  lamp  and  pays  for  itself  many 
times  as  a  place  to  attach  the  vacuum-cleaner  from 
which  all  the  rooms  on  that  floor  may  be  served.  In 
vestibules  and  on  porches  ceiling  fixtures  controlled  by 
means  of  convenient  switches  are  satisfactory.  The 
entrance  hall  may  be  made  to  express  hospitality  by 
means  of  lighting  which  should  be  adequate  and 
artistic. 

An  adequate  supply  of  outlets  and  wall  switches  is 
not  costly  and  they  pay  generous  dividends.  With  a 
scanty  supply  of  these,  the  possibilties  of  lighting  are 
very  much  curtailed.  There  is  nothing  intricate  about 
locating  switches  and  outlets,  so  the  householder  may 
do  this  himself,  or  he  may  view  critically  the  plans  as 
submitted.  The  chief  difficulties  are  to  throw  aside  his 
indifference  and  to  readjust  his  ideas  and  values.  It 


338 


ARTIFICIAL  LIGHT 


may  be  confidently  stated  that  the  possibilities  of  light¬ 
ing  far  outrank  most  of  the  features  which  contribute 
to  the  cost  of  a  house  and  of  its  furnishings. 

After  considering  the  requirements  and  decorative 
schemes  of  the  various  rooms  the  householder  should 
be  competent  to  judge  the  appropriateness  of  the  light¬ 
ing  effects  obtained  from  fixtures  which  the  dealer  dis¬ 
plays,  but  he  should  insist  upon  a  demonstration.  If 
the  dealer  is  not  equipped  with  a  room  for  this  purpose, 
he  should  be  asked  to  demonstrate  in  the  rooms  to  be 
lighted.  If  the  fixture-dealer  does  not  realize  that  he 
should  be  selling  lighting  effects,  the  householder 
should  make  him  understand  that  lighting  effects  are 
of  primary  importance  and  the  fixtures  themselves  are 
of  secondary  interest  in  most  cases.  The  unused  out¬ 
lets  that  have  been  installed  for  possible  future  needs 
may  be  sealed  in  plastering  if  the  positions  are  marked 
so  that  they  may  be  found  when  desired. 

An  advantage  of  portable  lamps  is  that  they  may  be 
taken  away  on  moving.  In  fact,  when  lighting  is 
eventually  considered  a  powerful  decorative  medium, 
as  it  should  be,  it  is  probable  that  fixtures  will  be  per¬ 
sonal  property  attached  to  ceiling,  wall,  and  floor  out¬ 
lets  by  means  of  plugs. 

A  variety  of  incandescent  lamps  are  available.  For 
the  home,  opal,  frosted,  or  bowl-frosted  lamps  are  usu¬ 
ally  more  satisfactory  than  clear  lamps.  Bare  fila¬ 
ments  should  not  be  visible,  for  they  not  only  cause  dis¬ 
comfort  and  eye-strain  but  they  spoil  what  might  other¬ 
wise  be  an  artistic  effect.  Lamps  with  diffusing  bulbs 
do  much  toward  eliminating  harsh  shadows  cast  by  the 


LIGHTING  THE  HOME 


339 


edges  of  the  shades,  by  the  chains  of  the  fixtures,  etc. 
These  lamps  are  available  in  many  shapes  and  sizes  and 
the  householder  should  make  a  record  of  voltage,  watt¬ 
age,  and  shape  of  the  lamps  which  he  finds  satisfactory 
in  the  various  fixtures.  The  Mazda  daylight  lamp  has 
several  places  in  the  home  and  the  Mazda  white-glass 
and  other  high-efficiency  lamps  supply  many  needs 
better  than  the  vacuum  lamps.  In  brackets  and  other 
purely  decorative  lighting-units  small  frosted  lamps 
are  usually  the  most  satisfactory.  There  is  a  general 
desire  for  the  warm  yellowish  light  of  the  candle-flame, 
and  this  may  be  obtained  by  a  tinted  shade  but  usually 
more  satisfactorily  by  means  of  a  tinted  lamp. 

The  householder  will  find  it  interesting  to  become  in¬ 
timate  with  lighting,  for  it  can  serve  him  well.  The 
housewife  will  often  find  much  interest  in  making 
shades  of  textiles  and  of  parchment.  Charming  glass¬ 
ware  in  appropriate  tints  and  painted  designs  is  avail¬ 
able  for  all  rooms.  In  the  bedchamber  and  the  nursery 
some  of  these  painted  designs  are  exceedingly  effective. 
Fixtures  should  shield  the  lamps  from  the  eyes,  and  the 
diffusing  media  whether  glass  or  textile  should  be  dense 
enough  to  prevent  glare.  No  fixture  can  be  beautiful 
and  no  lighting  effect  can  be  artistic  if  glare  is  present. 
If  the  architect  and  the  householder  will  realize  that 
light  is  a  medium  comparable  with  the  decorator’s 
media,  better  lighting  will  result.  Light  has  the  great 
advantage  of  being  mobile  and  with  adequate  outlets 
and  controls  supplemented  by  fixtures  from  which  dif¬ 
ferent  effects  are  available,  the  householder  will  find  in 
lighting  one  of  the  most  fruitful  sources  of  interest  and 


340 


ARTIFICIAL  LIGHT 


pleasure.  It  can  do  much  toward  expressing  the  taste 
of  the  householder  or  if  neglected  it  can  undo  much 
of  the  effect  of  excellent  decoration  and  furnishing. 
Artificial  lighting,  softly  diffused  and  properly  local¬ 
ized,  is  one  of  the  most  important  factors  in  making  a 
house  a  home. 


XXV 

LIGHTING— A  FINE  ART? 

In  the  preceding  chapters  the  progress  of  light  has 
been  sketched  from  its  obscure  infancy  to  its  vigorous 
youth  of  the  present  time.  It  has  been  seen  that  prog¬ 
ress  was  slow  until  the  beginning  of  the  nineteenth  cen¬ 
tury,  after  which  it  began  to  gain  momentum  until  the 
present  century  has  witnessed  tremendous  advances. 
Until  the  latter  part  of  the  nineteenth  century  artifi¬ 
cial  light  was  considered  an  expensive  utility,  but  as 
modern  lamps  appeared  which  supplied  adequate  light 
at  reasonable  cost  attention  began  to  be  centered  upon 
utilization,  and  the  lighting  engineer  was  born.  Gradu¬ 
ally  it  is  being  realized  that  artificial  light  is  no  longer 
a  luxury,  that  it  may  be  used  in  great  quantity,  and 
that  it  may  be  directed,  diffused,  and  altered  in  color 
as  desired.  Although  the  potentiality  of  light  has  been 
barely  drawn  upon,  the  present  usages  surpass  the 
most  extravagant  dreams  of  civilized  beings  a  half- 
century  ago.  Mere  light  of  that  time  was  changed  into 
more  light  as  gas-ligliting  developed,  and  more  light 
has  increased  to  adequate  light  of  the  present  time 
through  the  work  of  scientists. 

It  is  apparent  that  a  sudden  enforced  reversion  to 
the  primitive  flames  of  fifty  years  ago  would  paralyze 
many  activities.  Much  of  interest  and  beauty  would  be 

blotted  out  of  this  brilliant,  pulsating,  productive  age. 

341 


342 


ARTIFICIAL  LIGHT 


It  is  startling  to  note  that  almost  the  entire  progress 
in  artificial  lighting  has  taken  place  during  the  past 
hundred  years  and  that  most  of  it  has  been  crowded 
into  the  latter  part  of  this  period.  In  fact,  its  de¬ 
velopment  since  it  began  in  earnest  has  gone  forward 
with  ever-increasing  momentum.  On  viewing  the  won¬ 
ders  of  modern  artificial  lighting  on  every  hand  it  is 
not  difficult  to  muster  the  courage  necessary  to  venture 
into  its  future. 

The  lighting  engineer  has  been  a  natural  evolution 
of  the  present  age,  for  the  economic  aspects  of  lighting 
have  demanded  attention.  He  is  increasing  the  safety, 
efficiency,  and  happiness  of  mankind  and  civilization  is 
beginning  to  feel  his  influence  economically.  However, 
with  the  advent  of  adequate,  efficient,  and  controllable 
light,  the  potentiality  of  light  as  an  artistic  medium 
may  be  drawn  upon  and  the  lighting  artist  with  a  deep 
insight  into  the  possibilities  of  artificial  light  now  has 
his  opportunity.  But  the  artist  who  believes  that  a 
new  art  may  be  evolved  to  perfection  in  a  few  years 
is  doomed  to  disappointment,  for  it  is  necessary  only  to 
view  retrospectively  such  arts  as  painting  and  music  to 
be  convinced  that  understanding  and  appreciation  de¬ 
velop  slowly  through  centuries  of  experiment  and  con¬ 
tact. 

Will  lighting  ever  become  a  fine  art?  Will  it  ever 
be  able  alone  to  arouse  emotional  man  as  do  the  fine 
arts?  Are  the  powers  of  light  sufficiently  great  to  en¬ 
thrall  mankind  without  the  aid  of  form,  music,  action, 
or  spoken  words?  It  is  safer  to  answer  “yes”  than 
“no”  to  these  questions.  Painting  has  reached  a  high 
place  as  an  art  and  this  art  is  the  expressiveness  of 


LIGHTING— A  FINE  ART? 


343 


secondary  or  reflected  light  reinforced  by  imitation 
forms,  which  by  a  combination  of  light  and  drawing 
comprise  the  “  subjects.  ”  A  painting  is  a  momentary 
expression  of  light,  a  cross-section  of  something  mo¬ 
bile,  such  as  nature,  thought,  or  action.  Light  has  the 
essential  qualifications  of  painting  with  the  advantages 
of  a  greater  range  of  brightness,  of  greater  purity  of 
colors,  and  the  great  potentiality  of  mobility.  If  light¬ 
ing  becomes  a  fine  art  it  will  doubtless  be  related  to 
painting  somewhat  in  the  same  manner  that  architec¬ 
ture  is  akin  to  sculpture.  With  the  introduction  of 
mobility  it  will  borrow  something  from  the  arts  of  suc¬ 
cession  and  especially  from  music. 

The  art  of  lighting  in  its  present  infancy  is  leaning 
upon  established  arts,  just  as  the  infant  learns  to  walk 
alone  by  first  depending  upon  support.  The  use  of 
color  in  painting  developed  slowly,  being  supported  for 
centuries  by  the  strength  of  drawing  or  subject.  The 
landscapes  of  a  century  ago  were  dull,  for  color  was 
employed  hesitatingly  and  sparingly.  The  colors  in 
the  portraits  of  the  past  merely  represented  the  gor¬ 
geous  dress  of  bygone  days.  But  the  painter  of  the 
present  shows  that  color  is  beginning  to  be  used  for 
itself  and  that  the  painter  is  no  longer  hesitant  concern¬ 
ing  its  power  to  go  hand  in  hand  with  drawing.  Draft¬ 
ing  and  coloring  are  now  in  partnership,  the  former 
having  given  up  guardianship  when  the  latter  reached 
maturity. 

Lighting  is  now  an  accompaniment  of  the  drama,  of 
the  dance,  of  architecture,  of  decoration,  and  of  music. 
It  has  been  a  background  or  a  part  of  the  “atmos¬ 
phere”  excepting  occasionally  when  some  one  with 


344 


ARTIFICIAL  LIGHT 


imagination  and  daring  has  given  it  the  leading  role. 
Even  in  its  infancy  it  has  on  occasions  performed  ad¬ 
mirably  almost  without  any  aid.  The  bursting  rocket, 
the  marvelous  effects  at  the  Panama-Pacific  Exposi¬ 
tion,  and  some  of  the  exhibitions  on  the  theatrical  stage 
are  glimpses  of  the  potentiality  of  light.  To  fall  back 
upon  the  terminology  of  music,  these  may  he  glimmer¬ 
ings  of  light-symphonies. 

Harmony  is  simultaneity  and  a  painting  in  this  re¬ 
spect  is  a  chord — a  momentary  expression  fixed  in  ma¬ 
terial  media.  A  melody  of  light  requires  succession 
just  as  the  melody  in  music.  The  restless  colors  of  the 
opal  comprise  a  light  melody  like  the  songs  of  birds. 
The  gorgeous  splendor  of  the  sunset  compares  in  mag¬ 
nitude  and  in  its  various  moods  with  the  symphony 
orchestra  and  its  powers.  Throughout  nature  are  to 
be  found  gentle  chords,  beautiful  melodies  and  power¬ 
ful  symphonies  of  light  and  this  music  of  light  exhibits 
the  complexity  and  structure  analogous  to  music. 
There  is  no  physical  relation  between  music,  poetry, 
and  light,  but  it  is  easy  to  lean  upon  the  established 
terminology  for  purposes  of  discussion.  Those  who 
would  build  color-music  identical  to  sound  music  are 
making  the  mistake  of  starting  with  a  physical  founda¬ 
tion  instead  of  basing  the  art  of  light-expression  upon 
psychological  effects  of  light.  In  other  words,  a  rela¬ 
tion  between  light  and  music  can  exist  only  in  the 
psychological  realm. 

These  melodies  and  symphonies  of  light  in  nature  are 
admittedly  pleasing  or  impressive  as  the  case  may  be, 
but  are  they  as  appealing  as  music,  poetry,  painting, 
or  sculpture?  The  consensus  of  opinion  of  a  large 


LIGHTING— A  FINE  ART? 


345 


group  of  average  persons  might  indicate  a  negative 
reply,  but  the  combined  opinion  of  this  group  is  not  so 
valuable  as  the  opinion  of  a  colorist  or  of  an  artist  who 
has  sensed  the  wonders  of  light.  The  unprejudiced 
opinion  of  artists  is  that  light  is  a  powerfully  expres¬ 
sive  and  impressive  medium.  The  psychologist  will 
likely  state  that  the  emotive  value  of  light  or  color  is 
not  comparable  to  the  appeal  of  an  excellent  dinner  or 
of  many  other  commonplace  things.  But  he  has  ex¬ 
perimented  only  with  single  colors  or  with  simple  pat¬ 
terns  and  his  subjects  are  selected  more  or  less  at  ran¬ 
dom  from  the  multitude.  What  would  be  his  conclu¬ 
sion  if  he  examined  painters  and  others  who  have  de¬ 
veloped  their  sensibilities  to  a  deep  appreciation  of 
light  and  color?  It  is  certain  that  the  painter  who 
picks  up  a  purple  petal  fallen  from  a  rose  and  places 
it  upon  a  green  leaf  is  as  thrilled  by  the  powerful 
vibrant  color-chord  as  the  musician  who  hears  an  ex¬ 
quisite  harmony  of  sounds. 

Music  has  been  presented  to  civilized  mankind  in  an 
organized  manner  for  ages  and  the  fundamental  physi¬ 
cal  basis  of  modern  music  is  a  thousand  years  old. 
Would  the  primitive  savage  appreciate  the  modern 
symphony  orchestra?  Even  the  majority  of  civilized 
beings  prefer  the  modern  ragtime  or  jazz  to  the  ex¬ 
quisite  art  of  the  symphony.  An  appreciation  of  the 
opera  and  the  symphony  is  reached  by  educational 
methods  extending  over  long  periods.  An  apprecia¬ 
tion  of  the  expressiveness  of  light  cannot  be  expected 
to  be  realized  by  any  short-cut.  Most  persons  to-day 
enjoy  the  melodramatic  4  ‘  movie  ”  more  than  the  drama 
and  relatively  few  experience  the  deep  appeal  of  the 


346 


ARTIFICIAL  LIGHT 


fine  arts.  Surely  the  symphony  of  light  cannot  be 
justly  condemned  because  of  a  lack  of  appreciation  and 
understanding  of  it,  for  it  has  not  been  introduced  to 
the  public.  Furthermore,  the  expressiveness  of  music 
is  still  indefinite  at  best  despite  the  many  centuries  of 
experimenting  on  the  part  of  musicians. 

If  poetry  is  to  be  believed,  the  symphonies  of  light 
as  rendered  by  nature  in  the  sunsets,  in  the  aurora 
borealis,  and  in  other  sky-effects  of  great  magnitude 
have  deeply  impressed  the  poet.  If  his  descriptions 
are  to  be  accepted  at  their  face-value,  the  melodies  of 
light  rendered  in  the  precious  stone,  in  the  ice-crystal, 
and  in  the  iridescence  of  bird-plumage  please  his 
finer  sensibilities.  If  he  is  sincere,  mobile  light  is  a 
seductive  agency. 

The  painter  has  contributed  little  of  direct  value  in 
developing  the  music  of  light.  He  is  concerned  with 
an  instantaneous  expression.  He  waits  for  it  patiently 
and,  while  waiting,  learns  to  appreciate  the  fickleness  of 
mood  in  nature,  but  when  he  fixes  one  of  these  moods 
he  has  contributed  very  little  to  the  art  of  mobile  light. 
Unfortunately  the  art  schools  teach  the  student  little 
or  nothing  pertaining  to  color  for  color’s  sake.  When 
the  student  is  capable  of  drawing  fairly  well  and  is  ac¬ 
quainted  with  a  few  stereotyped  principles  of  color- 
harmony  he  is  sent  forth  to  follow  in  the  footsteps  of 
past  masters.  He  may  be  seen  at  the  art  museum  faith¬ 
fully  copying  a  famous  painting  or  out  in  the  fields 
stalking  a  tree  with  the  hopes  of  an  embryo  Corot. 
The  world  moves  and  has  only  a  position  in  the  rank 
and  file  for  imitators.  Occasionally  an  artist  goes  to 
work  with  a  vim  and  indulges  in  research,  thereby 


LIGHTING— A  FINE  ART? 


347 


demonstrating  originality  in  two  respects.  Painting  is 
just  as  much  a  field  for  research  as  light-production. 

Recently  experiments  are  being  made  in  the  produc¬ 
tion  of  color-harmonies  devoid  of  form.  Surely  there 
is  a  field  for  pure  color-composition  and  this  the  field  of 
the  painter  which  leads  toward  the  art  of  mobile  light. 
Many  of  the  formless  paintings  of  the  present  day 
which  pass  under  the  banner  of  this  ism  or  that  are 
merely  experiments  in  the  expressiveness  of  light.  Be¬ 
ing  formless,  they  are  devoid  of  subject  in  the  ordinary 
sense  and  cannot  be  more  or  less  than  a  fixed  expres¬ 
sion  of  light.  Naturally  they  have  received  much  criti¬ 
cism  and  have  been  ridiculed,  but  they  can  expect  noth¬ 
ing  else  until  they  are  understood.  They  cannot  be 
understood  until  mankind  learns  their  language  and 
then  they  must  be  understandable.  In  other  words, 
there  are  impostors  gathered  around  the  sincere  re¬ 
search-artist  because  the  former  have  neither  the  abil¬ 
ity  to  paint  for  a  living  nor  the  inclination  to  forsake 
the  comparative  safety  of  the  mystery  of  art  for  the 
practical  world  where  their  measure  would  be  quickly 
taken.  This  army  of  camp-followers  will  not  advance 
the  art  of  mobile  light,  but  the  sincere  seekers  after 
the  principles  of  light-expression  who  form  the  founda¬ 
tion  of  the  various  isms  may  contribute  much. 

The  painter  will  always  be  available  with  his  finer 
sensibility  to  appreciate  and  to  aid  in  developing  the 
art  of  mobile  light,  but  his  direct  contribution  appears 
most  likely  to  come  from  the  present  chaos  of  experi¬ 
ments  in  pure  color-composition,  in  the  psychology  of 
light,  or,  more  broadly,  in  the  expressiveness  of  light. 
The  decorator  and  the  designer  of  gowns  and  cos- 


348 


ARTIFICIAL  LIGHT 


tumes  do  not  arrogate  to  themselves  the  name  “artist,” 
but  they  are  daily  creating  something  which  is  leading 
toward  a  fuller  appreciation  of  the  expressiveness  of 
light.  If  they  do  not  contribute  directly  to  the  develop¬ 
ment  of  the  art  of  mobile  light,  they  are  at  least  aiding 
in  developing  what  may  eventually  be  an  appreciative 
public. 

The  artist  paints  a  “still-life,”  the  decorator  creates 
a  color-harmony  of  abstract  or  conventional  forms,  and 
the  costumer  produces  a  color-composition  in  textiles. 
The  decorator  and  costumer  approach  closer  to  pure 
color-composition  than  the  artist  in  his  still-life.  The 
latter  is  a  grouping  of  objects  primarily  for  their  color- 
notes.  Why  bother  with  a  banana  when  a  yellow-note 
is  desired?  Why  utilize  the  abstract  or  conventional 
forms  of  the  decorator?  Why  not  follow  this  lead  fur¬ 
ther  to  the  less  definite  forms  employed  by  the  cos¬ 
tumer?  Why  not  eliminate  form  even  more  com¬ 
pletely?  This  is  an  important  point  and  an  interesting 
lead,  for  to  become  rid  of  form  has  been  one  of  the 
perplexing  problems  encountered  by  those  who  have 
dreamed  of  an  art  of  mobile  light. 

The  painter  who  uses  line  and  color  imitatively  has 
perhaps  acquired  skill  in  depicting  objects  and  more  or 
less  appreciation  of  the  beautiful.  But  if  he  is  to  be 
creative  and  to  produce  a  higher  art  he  must  be  able  to 
use  line  and  color  without  reference  to  objects.  He 
thus  may  aid  in  the  development  of  an  abstract  art 
which  is  the  higher  art  and  at  the  same  time  aid  in 
educating  the  public  to  appreciate  pure  color-har¬ 
monies.  From  these  momentary  expressions  of  light 
and  from  the  experience  gained,  the  mobile  colorist 


LIGHTING— A  FINE  ART! 


349 


would  receive  material  aid  and  his  productions  would 
be  viewed  by  a  more  receptive  audience  or  rather 
“optience”  as  it  may  be  called.  The  development  of 
taste  for  abstract  art  is  needed  in  order  that  the  art 
of  mobile  light  may  develop  and,  incidentally,  an  appre¬ 
ciation  of  the  abstract  in  art  is  needed  in  all  arts. 

Science  has  contributed  much  by  way  of  clearing  the 
decks.  It  has  produced  the  light-sources  and  the  ap¬ 
paratus  for  controlling  light.  It  has  analyzed  the 
physical  aspects  of  color-mixture  and  has  accumulated 
extensive  data  pertaining  to  color-vision.  It  has 
pointed  out  pitfalls  and  during  recent  years  has  been 
delving  further  by  investigating  the  psychology  of 
light  and  color.  The  latter  field  is  looked  to  for  valu¬ 
able  information,  but,  after  all,  there  is  one  way  of  mak¬ 
ing  progress  in  the  absence  of  data  and  that  is  to  make 
attempts  at  the  production  of  impressive  effects  of 
mobile  light.  Some  of  these  have  been  made,  but  un¬ 
fortunately  they  have  been  heralded  as  finished  prod¬ 
ucts. 

Perhaps  the  most  general  mistake  made  is  in  relating 
sounds  and  colors  by  stressing  a  mere  analogy  too 
far.  Notwithstanding  the  vibratory  nature  of  the 
propagation  of  sound  and  light,  this  is  no  reason  for 
stressing  a  helpful  analogy.  After  all  it  is  the  psycho¬ 
logical  effect  that  is  of  importance  and  it  is  absurd  to 
attribute  any  connection  between  light-waves  and 
sound-waves  based  upon  a  relation  of  physical  quanti¬ 
ties.  No  space  will  be  given  to  such  a  relation  because 
it  is  so  absurdly  superficial ;  however,  the  language  of 
music  will  be  borrowed  with  the  understanding  that  no 
relation  is  assumed. 


350 


ARTIFICIAL  LIGHT 


A  few  facts  pertaining  to  vision  will  indicate  the 
trend  of  developments  necessary  in  the  presentation  of 
mobile  light.  The  visual  process  synthesizes  colors 
and  at  this  point  departs  widely  from  the  auditory 
process.  The  sensation  of  white  may  be  due  to  the 
synthesis  of  all  the  spectral  colors  in  the  proportions 
in  which  they  exist  in  noon  sunlight  or  it  may  be  due 
to  the  synthesis  of  proper  proportions  of  yellow  and 
blue,  of  red,  green,  and  blue,  of  purple  and  green,  and  a 
vast  array  of  other  combinations.  A  mixture  of  red 
and  green  lights  may  produce  an  exact  match  for  a  pure 
yellow.  Thus  it  is  seen  that  the  mixture  of  lights  will 
cause  some  difficulty.  For  example,  the  components  of 
a  musical  chord  may  be  picked  out  one  by  one  by  the 
trained  ear,  but  if  two  or  more  colored  lights  are  mixed 
they  are  merged  completely  and  the  resultant  color  is 
generally  quite  different  from  any  of  the  components. 
In  music  of  light,  the  components  of  color-chords  must 
be  kept  separated,  for  if  they  are  intermingled  like 
those  of  musical  chords  they  are  indistinguishable. 
Therefore,  the  elements  of  harmony  in  mobile  light 
must  be  introduced  by  giving  the  components  different 
spatial  positions. 

The  visual  process  is  more  sluggish  than  the  audi¬ 
tory  process;  that  is,  lights  must  succeed  each  other 
less  rapidly  than  musical  notes  if  they  are  to  be  dis¬ 
tinguished  separately.  The  ear  can  follow  the  most 
rapid  execution  of  musical  passages,  but  there  is  a 
tendency  for  colors  to  blend  if  they  follow  one  another 
rapidly.  This  critical  frequency  or  rate  at  which  suc¬ 
cessive  colors  blend  decreases  with  the  brightness  of 
the  components.  If  red  and  green  are  alternated  at  a 


LIGHTING — A  FINE  ART! 


351 


rate  exceeding  the  critical  frequency,  a  sensation  of 
yellow  will  result;  that  is,  neither  component  will  be 
distinguishable  and  a  steady  yellow  or  a  yellow  of 
flickering  brightness  will  be  seen.  The  hues  blend  at 
a  lower  frequency  than  the  brightness  components  of 
colors ;  hence  there  may  be  a  blend  of  color  which  still 
flickers  in  brightness.  Many  weird  results  may  be  ob¬ 
tained  by  varying  the  rate  of  succession  of  colors.  If 
this  rate  is  so  low  that  the  colors  do  not  tend  to  merge, 
they  are  much  enriched  by  successive  contrast.  It  is 
known  that  juxtaposed  colors  generally  enrich  one  an¬ 
other  and  this  phenomenon  is  known  as  simultaneous 
contrast.  Successive  contrast  causes  a  similar  effect 
of  heightened  color. 

An  effect  analogous  to  dynamic  contrast  in  music 
may  be  obtained  with  mobile  light  by  varying  the  in¬ 
tensity  of  the  light  or  possibly  the  area.  Melody  may 
be  simply  obtained  by  mere  succession  of  lights.  Tone- 
quality  has  an  analogy  in  the  variation  of  the  purity  of 
color.  For  example,  a  given  spectral  hue  may  be  con¬ 
verted  into  a  large  family  of  tints  by  the  addition  of 
various  amounts  of  white  light.  Rhythm  is  as  easily 
applied  to  light  as  to  music,  to  poetry,  to  pattern,  or 
to  the  dance,  but  in  mobile  lights  its  limitations  already 
have  been  suggested.  However,  it  is  bound  to  play  an 
important  part  in  the  art  of  mobile  light  because  rhyth¬ 
mic  experiences  are  much  more  agreeable  than  those 
which  are  non-rhythmic.  Rhythm  abounds  everywhere 
and  nothing  so  stirs  mankind  from  the  lowliest  savage 
to  the  highly  cultivated  being  as  rhythmic  sequences. 

Many  psychological  effects  of  light  have  been  re¬ 
corded  from  experiment  and  observation  and  affective 


352 


ARTIFICIAL  LIGHT 


values  of  light  have  been  established  in  various  other 
byways.  It  is  possible  that  the  degree  of  pleasure  ex¬ 
perienced  by  most  persons  on  viewing  a  color-harmony 
or  the  delightful  color-melody  of  a  sunlit  opal  may  be 
less  than  that  experienced  on  listening  to  the  rendition 
of  music.  However,  if  this  were  true  it  would  offer 
no  discouragement,  because  absolute  values  play  a 
small  part  in  life.  Two  events  when  directly  compared 
apparently  may  differ  enormously  in  their  ability  to 
arouse  emotions,  but  the  human  organism  is  so  adapt¬ 
ive  that  each  in  its  proper  environment  may  power¬ 
fully  affect  the  emotions.  For  example,  those  who 
have  sported  in  aerial  antics  in  the  heights  of  cloudland 
or  have  stormed  the  enemy’s  trench  are  still  capable  of 
enjoying  a  sunset  or  the  call  of  a  bird  to  its  mate  at 
dusk.  The  wonderful  adaptability  of  the  inner  being 
is  the  salvation  of  art  as  well  as  of  life,. 

In  the  rendition  of  mobile  light  it  is  fair  to  give  the 
medium  every  advantage.  Sometimes  this  means  to 
eliminate  competitors  and  sometimes  it  means  to  re¬ 
move  handicaps.  On  the  stage  light  has  had  com¬ 
petitors  which  are  better  understood.  For  example, 
in  the  drama  words  and  action  are  easily  understood, 
and  regardless  of  the  effectiveness  of  light  it  would  not 
receive  much  credit  for  the  emotive  value  of  the  produc¬ 
tion.  In  the  wonderful  harmony  of  music,  dance,  and 
light  in  certain  recent  exhibitions,  the  dance  and  music 
overpowered  the  effects  of  lights  because  they  speak 
familiar  languages. 

A  number  of  attempts  have  been  made  to  utilize  light 
as  an  accompaniment  of  music  and  some  of  them  on  a 
small  scale  have  been  sincere  and  creditable,  but  a 


A  community  Christmas  tree 


A  community  song-festival 


ARTIFICIAL  LIGHT  IN  COMMUNITY  AFFAIRS 


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LIGHTING— A  FINE  ART? 


353 


much-heralded  exhibition  on  a  large  scale  a  few  years 
ago  was  not  the  product  of  deep  thought  and  sincere 
effort.  For  example,  colored  lights  thrown  upon  a 
screen  having  an  area  of  perhaps  twenty  square  feet 
were  expected  to  compete  with  a  symphony  orchestra 
in  Carnegie  Hall.  The  music  reached  the  most  dis¬ 
tant  auditor  in  sufficient  volume,  but  the  lighting  effect 
dwindled  to  insignificance.  Without  entering  into  cer¬ 
tain  details  which  condemned  the  exhibition  in  advance, 
the  method  of  rendition  of  the  light-accompaniment  re¬ 
vealed  a  lack  of  appreciation  of  the  problems  involved 
on  the  part  of  those  responsible. 

Incidentally,  it  has  been  shown  that  the  composer 
of  this  particular  musical  selection  with  its  light  ac¬ 
companiment  was  psychologically  abnormal;  that  is, 
he  was  affected  with  colored  audition.  It  is  not  yet 
established  to  what  extent  normal  persons  are  simi¬ 
larly  affected  by  light  and  color.  Certainly  there  is 
no  similarity  among  the  abnormal  and  none  between 
the  abnormal  and  normal. 

If  light  is  to  be  used  as  an  accompaniment  to  music, 
it  must  be  given  an  opportunity  to  supply  “atmos¬ 
phere.”  This  it  cannot  do  if  confined  to  an  insignifi¬ 
cant  spot;  it  must  be  given  extensity.  Furthermore, 
by  the  use  of  diaphanous  hangings,  form  will  be  mini¬ 
mized  and  the  evanescent  effects  surely  can  be  charm¬ 
ing.  But  finally  the  lighting  effects  must  fill  the  field 
of  vision  just  as  the  music  “fills  the  field  of  audition” 
in  order  to  be  effective.  There  are  fundamental  ob¬ 
jections  to  the  use  of  mobile  light  as  an  accompaniment 
to  music  and  therefore  the  future  of  the  art  of  mobile 
light  must  not  be  allowed  to  rest  upon  its  success  with 


354 


ARTIFICIAL  LIGHT 


music.  If  it  progresses  through  its  relation  with 
music,  so  much  is  gained;  if  not,  the  relation  may  be 
broken  for  music  is  quite  capable  of  standing  alone. 

There  is  a  tendency  on  the  part  of  some  revolution¬ 
ary  stage  artists  to  give  to  lighting  an  emotional  part 
in  the  play,  or,  in  other  words,  to  utilize  lighting  in 
obtaining  the  proper  mood  for  the  action  of  the  play. 
Color  and  purely  pictorial  effect  are  the  dominant 
notes  of  some  of  them.  All  of  these  modern  stage-art¬ 
ists  are  abandoning  the  intricately  realistic  setting, 
and,  as  a  consequence,  light  is  enjoying  a  greater  op¬ 
portunity.  In  the  more  common  and  shallow  theatri¬ 
cal  production,  lighting  and  color  effects  have  many 
times  saved  the  day,  and,  although  these  effects  are 
not  of  the  deeper  emotional  type,  they  may  add  a  spec¬ 
tacular  beauty  which  brings  applause  where  the  sing¬ 
ing  is  mediocre  and  the  comedy  isn’t  comedy.  The 
potentiality  of  lighting  effects  for  the  stage  has  been 
barely  drawn  upon,  but  as  the  expressiveness  of  light 
is  more  and  more  utilized  on  the  stage,  the  art  of  mo¬ 
bile  light  will  be  advanced  just  so  much  more.  Light, 
color,  and  darkness  have  many  emotional  suggestions 
which  are  easily  understood  and  utilized,  but  the  blend¬ 
ing  of  mobile  light  with  the  action  is  difficult  because 
its  language  is  only  faintly  understood. 

It  is  futile  to  attempt  to  describe  a  future  composi¬ 
tion  of  mobile  light.  Certainly  there  is  an  extensive 
variety  of  possibilities.  A  sunset  may  be  compressed 
into  minutes  or  an  opalescent  sky  may  be  a  motif. 
Varying  intensities  of  a  single  hue  or  of  allied  hues 
may  serve  as  a  gentle  melody.  Realistic  effects  may 


LIGHTING— A  FINE  ART? 


355 


be  introduced.  The  expressiveness  of  individual  col¬ 
ors  may  be  taken  as  a  basis  for  constructing  the  va¬ 
rious  motifs.  These  may  be  woven  into  melody  in 
which  rhythm  both  in  time  and  in  intensity  may  be  in¬ 
troduced.  Action  may  be  easily  suggested  and  the 
number  of  different  colors,  in  a  broad  sense,  which  are 
visible  is  comparable  to  the  audible  tones.  Shading  is 
as  easily  accomplished  as  in  music  and  the  develop¬ 
ment  of  this  art  need  not  be  inhibited  by  a  lack  of 
mechanical  devices  and  light-sources.  The  tools  will 
be  forthcoming  if  the  conscientious  artist  requests 
them. 

Whatever  the  future  of  the  art  of  mobile  light  may 
be,  it  is  certain  that  the  utilization  of  the  expressive¬ 
ness  of  light  has  barely  begun.  It  may  be  that  light- 
music  must  pass  through  the  “ragtime”  stage  of  fire¬ 
works  and  musical-revue  color-effects.  If  so,  it  is 
gratifying  to  know  that  it  is  on  its  way.  Certainly  it 
has  already  served  on  a  higher  level  in  some  of  the  ar¬ 
tistic  lighting  effects  in  which  mobility  has  featured  to 
some  extent. 

If  the  art  does  not  develop  rapidly  it  will  be  merely 
following  the  course  of  other  arts.  A  vast  amount  of 
experimenting  will  be  necessary  and  artists  and  public 
alike  must  learn.  But  if  it  ever  does  develop  to  the 
level  of  a  fine  art  its  only  rival  will  be  music,  because 
the  latter  is  the  only  other  abstract  art.  Material  civ¬ 
ilization  has  progressed  far  and  artificial  light  has 
been  a  powerful  influence.  May  it  not  be  true  that 
artificial  light  will  be  responsible  for  the  development 
of  spiritual  civilization  to  its  highest  level?  If  mobile 


356 


ARTIFICIAL  LIGHT 


light  becomes  a  fine  art,  it  will  be  man’s  most  abstract 
achievement  in  art  and  it  may  be  incomparably  finer 
and  more  ethereal  than  music.  If  this  is  realized,  arti¬ 
ficial  light  in  every  sense  may  well  deserve  to  be  known 
as  the  torch  of  civilization. 


READING  REFERENCES 

No  attempt  will  be  made  to  give  a  pretentious 
bibliography  of  the  literature  pertaining  to  the  va¬ 
rious  aspects  of  artificial  lighting,  for  there  are  many 
articles  widely  scattered  through  many  journals.  The 
Transactions  of  the  Illuminating  Engineering  Society 
afford  the  most  fruitful  source  of  further  information ; 
the  Illuminating  Engineer  (London),  contains  much  of 
interest;  and  Z eitschrift  fur  Beleuchtungswesen  deals 
with  lighting  in  Germany.  H.  R.  D’Allemagne  has 
compiled  an  elaborate  “Historie  du  Luminaire”  which 
is  profusely  illustrated,  and  L.  von  Benesch  in  his 
“Beleuchtungswesen”  has  presented  many  elaborate 
charts.  In  both  these  volumes  lighting  devices  and 
fixtures  from  the  early  primitive  ones  to  those  of  the 
nineteenth  century  are  illustrated.  A  few  of  the  latest 
books  on  lighting,  in  the  English  language,  are  “The 
Art  of  Illumination,”  by  Bell;  “Modern  Illuminants 
and  Illuminating  Engineering,”  by  Gaster  and  Dow; 
“Radiation,  Light  and  Illumination,”  by  Steinmetz; 
“The  Lighting  Art,”  by  Luckiesh;  “Illuminating  En¬ 
gineering  Practice,”  consisting  of  a  course  of  lectures 
presented  by  various  experts  under  the  joint  auspices 
of  the  University  of  Pennsylvania  and  the  Illuminating 
Engineering  Society;  “Lectures  on  Illuminating  En¬ 
gineering,”  comprising  a  series  of  lectures  presented 
under  the  joint  auspices  of  Johns  Hopkins  University 

357 


358 


ARTIFICIAL  LIGHT 


and  the  Illuminating  Engineering  Society;  and  “The 
Range  of  Electric  Searchlight  Projectors,”  by  Rey; 
“The  Electric  Arc/’  by  Mrs.  Ayrton;  “Electric  Arc 
Lamps/ *  by  Zeidler  and  Lustgarten,  and  “The  Elec¬ 
tric  Arc,”  by  Child  treat  the  scientific  and  technical 
aspects  of  the  arc.  G.  B.  Barham  has  furnished  a  book 
on  “The  Development  of  the  Incandescent  Electric 
Lamp.”  “Color  and  Its  Applications,”  and  “Light 
and  Shade  and  Their  Applications,”  are  two  books  by 
Luckiesh  which  deal  with  lighting  from  unique  points 
of  view.  “The  Language  of  Color,”  by  Luckiesh,  aims 
to  present  what  is  definitely  known  regarding  the  ex¬ 
pressiveness  and  impressiveness  of  color.  W.  P.  Ger¬ 
hard  has  supplied  a  volume  on  “The  American  Prac¬ 
tice  of  Gaspiping  and  Gas  Lighting  in  Buildings,”  and 
Leeds  and  Butterfield  one  on  “Acetylene.”  A  recent 
book  in  French  by  V.  Trudelle  treats  “Lumiere  Elec- 
trique  et  ses  differentes  Applications  an  Theatre.” 
Many  books  treat  of  photometry,  power-plants,  etc., 
but  these  are  omitted  because  they  deal  with  phases  of 
light  which  have  not  been  discussed  in  the  present 
volume.  “Light  Energy,”  by  Cleaves,  is  a  large  vol¬ 
ume  devoted  to  light-therapy,  germicidal  action  of 
radiant  energy,  etc.  References  to  individual  articles 
will  often  be  found  in  the  various  indexes  of  publica¬ 
tions. 


THE  END 


INDEX 


Aaron,  43 

Accidents:  8;  street-lighting  in  re¬ 
lation  to,  225  et  seq .;  percent¬ 
age  (table)  of,  due  to  improper 
lighting,  231 

Acetylene:  62;  light-yield  of,  106, 
107,  170,  187,  191 

Actinic  rays:  effect  of,  upon  hu¬ 
man  organism,  275 
Africa,  public  lighting  in  ancient, 
31 

Agni,  god  of  fire,  40 
Air-pump,  130 
Air-raids,  225 
Alaska,  18,  29 
Alchemy,  20 
Aleutians,  18 
Alexandria,  43,  163 
Allylene,  106 
Aluminum,  108,  179,  180 
Amiens,  Treaty  of,  69 
Amylene,  106 
Aniline  dyes,  106 

Animal:  distinction  between,  and 
human  being,  3;  15;  produc¬ 

tion  of  light,  24  et  seq.;  sources 
of  light,  30,  31;  oils,  51 
Antimony,  294 
Antioch,  153 
Arago,  114,  196 
Archbishop  of  Canterbury,  49 
Archimedes,  19 

Arc:  lamps,  69,  89;  electric,  111 
et  seq.;  distinction  between 
spark  and,  112;  Davy’s  notes  on 
electric,  113;  formation  of,  115, 
116;  Staite  and  enclosed,  117, 
118;  principle  of  enclosed,  118, 
119;  types  of,  120;  flame-,  121, 
122;  luminous,  122;  electric, 
127 ;  luminous  efficiency  of  elec¬ 
tric  (table),  124;  160  et  seq.; 
-lamp  in  lighthouses,  168  et  seq.; 
magnetite-,  187;  261 
Ardois  system  of  signaling,  199 


Argand,  Ami:  52;  inaugurates 
new  era  in  artificial  lighting,  53, 
54;  63,  70,  76,  77,  78,  97,  167, 
196 

Argon,  137 

Aristophanes,  “The  Clouds,”  19 
Art  Museums,  9,  13,  322,  323 
Asbestos,  170 

Asia :  public  lighting  in  ancient, 
31,  39 

Automobiles,  238 
Babylon,  39 

Bacteria:  effect  of  artificial  light 
upon,  272  et  seq.;  281,  282 
Bailey,  Prof.  L.  H.,  250 
Baltimore,  98 

Bamboo:  carbon  filaments,  169 
Bartholdi,  302,  303 
Beacons.  See  Lighthouses. 

Beck,  186 
Beecher,  72 
Beeswax,  35,  51 
Benzene,  106 

Bible,  cited  on  importance  of  arti¬ 
ficial  light,  42-44 
“Bluebird,  The,”  Maeterlinck,  9 
Blue-prints,  261 
Bollman,  98 
Bolton,  von,  132,  133 
Bombs,  illuminating,  182  et  seq. 
Boston  Light,  164,  165,  166,  177 
Bowditch,  production  of  regenera¬ 
tive  lamp  by,  78,  79 
Boy  Scouts,  17 
Bremer,  120 
Bristol  University,  252 
Brush,  68,  159 
Building,  8 

Bunsen,  81,  85,  89,  148,  149 
Bureau  of  Mines:  cited  on  open 
flames,  234;  236 

Burning-glasses,  19  20.  See  also 
Lenses. 

Butylene,  106 


INDEX 


360 

Byzantium,  34 

Caesar,  163 

Canada,  254 

Candle-hour,  defined,  215 
Candles:  progress  and,  7;  25,  28, 
29,  30,  33;  religious  uses  of, 
34,  35;  as  a  modern  light-source, 
36,  37 ;  ceremonial  uses  of,  38 
et  seq .;  44,  48,  57,  82,  97,  222, 
299,  304 

Calcium,  107,  108 
Carbolic  acid,  106 
Carbon:  53,  80,  81;  physical  char¬ 
acteristics  of,  80,  81;  90,  104, 
105,  128,  129,  144,  170 
Carbon  filament:  127  et  seq.; 
preparation  of,  129,  130,  131; 
luminous  efficiency  of,  131,  132; 
lamps,  161 ;  lamps  in  green¬ 
houses,  250  et  seq. 

Carbons,  formation  of,  115,  116 
Carbureted  hydrogen,  75 
Carcel,  invention  of  clockwork 
lamp  by,  54,  55 
Cat-gut,  130 
Ceria,  85,  101 
Charleston,  S.  C.,  185 
Charcoal:  113;  uses  of,  for  elec¬ 
trodes,  115 

Chartered  Gas  Light  and  Coke  Co., 
London,  74 

Chemistry:  artificial  light  and, 
256-268 

Chicago,  62,  304,  305 
Chimneys,  54,  60,  62 
China,  19,  31,  32 
Chlorate  of  potash,  22 
Christ,  33,  46,  47 
Christians,  “children  of  light,”  42 
Christmas  trees,  43,  304 
Chromium,  294 
Church  of  England,  49 
Cities:  economy  of  artificial  light¬ 
ing  in  congested,  13 
Civilization:  effect  of  artificial 
light  upon,  4  et  seq.;  fire  and, 
15 

Clark,  Parker  and,  139 
Clayton,  Dr.:  invention  of  portable 
gas-light  by,  64;  quoted,  64,  65; 
experiments  of,  with  coal-gas,  67 


Claude,  147 

Cleaves,  Dr.,  quoted,  276,  277 
Clegg,  Samuel:  74;  gas-lighting 
accomplishments  of,  75,  76 
Cleveland,  159 

“Clouds,  The,”  Aristophanes,  19 
Coal :  32 ;  as  a  light- source,  55 ; 
supply,  223;  228 

Coal-gas:  63  et  seq.;  public  light¬ 
ing  by,  developed,  70  et  seq.; 
analytical  production  of,  103, 
104;  yield  of,  retort  (table), 
105;  analysis  of,  106 
Coal-mines,  234  et  seq. 

Cobalt,  294 
Coke,  68,  105 
Cologne,  157,  158 
Colomb,  Philip,  197 
Color:  9;  relation  of  artificial 
light  to,  284  et  seq. 

Colza,  31,  52,  167 
Combustion,  82  et  seq. 

Commerce,  8,  97 
Constantine,  42 
Copper,  262,  295 
Cornwall,  63 

Cotton:  101;  carbon  filaments, 
129,  130 
Cromartie,  78 
Crookes,  90,  146 

Crosiey,  Samuel,  improvement  of 
gas-meter  by,  76 
Crusies,  32 


Daguerre,  258 
Dancing,  346 

Davy,  Sir  Humphrey:  33,  68,  73; 
first  use  by,  of  charcoal  for 
sparking  points,  112;  notes  of, 
on  electric  arc,  113;  114 
Daylight,  artificial,  12;  284  et 

seq.;  application  of,  287 
Daylighting,  12-14 
Dollond,  195 
Doty,  61,  167 

Drake,  Col.  E.  L.,  discovery  of  oil 
in  Pennsylvania  by,  56 
Drummond,  Thomas:  171,  185, 

196;  quoted  on  signaling,  197 
Dudgeon,  Miss,  251,  252 
Dyes,  256,  265 


INDEX  361 


East  Indies,  29 
Eddystone  Light,  166,  167 
Edison :  and  problem  of  electric  in¬ 
candescent  filament  lamps,  128 
et  seq .;  129;  quoted  on  birth  of 
incandescent  lamp,  130 
Edward  I,  274 
Edward  VI,  49 

Efficiency,  effect  of  artificial  light 
upon,  14 

Eggs:  relation  of  artificial  light  to 
production  of,  247,  248 
Egypt:  31;  sacredness  of  light  in 
ancient,  39;  153,  195 
Electric  filament:  81,  127  et  seq.; 
approximate  value  of,  lamps  (ta¬ 
ble),  138 

Electric  pile:  construction  of, 
111;  127 

Electricity:  13,  22;  as  a  light- 
source,  57 ;  for  home-lighting, 
62,  84;  87,  89;  ignition  of  gas 
by,  102;  lighting  by,  109  et  seq. 
Electromagnetic  waves,  68,  86,  87 
Electromagnets,  114,  116 
Electrodes,  113,  114,  115  et  seq.; 

life  of,  122 
Elizabeth,  Queen,  274 
England:  32;  petroleum  discov¬ 
ered  in,  56;  gas-lighting  in,  63 
et  seq.;  166,  251,  274 
Erbia,  85 

Esquimaux:  18;  use  of  artificial 
light  by,  31 
Ethylene,  106 


Factories:  13;  artificial  light  in, 
239  et  seq. 

Faraday,  113 

Filaments,  carbon,  129  et  seq. 

Finsen:  273,  274,  275;  on  stimu¬ 
lating  action  of  artificial  light, 
277;  279,  280 

Fire:  importance  of,  to  man,  5 
et  seq.;  man’s  dependence  upon, 
15;  mythical  origin  of,  16;  mak¬ 
ing,  17  et  seq.;  production  of,  in 
the  stone  age,  18;  in  early  civili¬ 
zation,  19;  ancient  worship  of, 
29,  299 

Fireflies:  24,  81,  96,  148,  149,  150 


“First  Men  in  the  Moon,  The,”  H. 

G,  Wells,  cited,  148 
Fish:  artificial  light  as  bait  for, 
249 

Flame-arcs,  120,  121,  122,  187 
Flames:  86,  88,  89;  open,  233,  234 
et  seq. 

Flint,  33 
Fool’s  gold,  18 
Fort  Wagner,  185 
France:  lamps  in,  55;  early  gas¬ 
light  in,  72 

Franchot,  invention  of  moderator 
lamps  by,  55 
Frankland,  77 

Franklin,  Benjamin:  165;  quoted, 
210-212;  213 
Fresnel,  167,  196 
Friction,  16,  17 

Gas:  13,  22;  discovery  of  coal,  32, 
33;  early  uses  of,  as  light-source, 
63  et  seq.;  installment  of,  pipes 
in  England,  63,  64;  Shirley’s  re¬ 
port  on  Natural,  66,  67 ;  first 
public  display  of,  lighting,  69; 
cost  of,  lighting,  71;  first  at¬ 
tempt  at  industrial,  lighting,  72: 
first  English,  company,  74;  first, 
explosion,  75;  house,  lighting, 
76,  77;  80,  82;  spectrum  of,  90; 
modern,  lighting  industry,  97 
et  seq.;  origin  of  lighting  by, 
98;  first,  works  in  America,  98; 
growth  of,  consumption  in 
United  States,  99;  electrical  ig¬ 
nition  applied  to,  lighting,  102; 
pressure,  102,  103;  water,  105; 
carbons  in,  106;  production  of 
Pintsch,  109,  110;  salts  applied 
to,  flames,  120;  157;  Census  Bu¬ 
reau  figures  on  cost  of,  plants, 
221,  222;  224,  341 
Gas-burners:  63,  64,  77;  candle- 
power  of  pioneer  (table),  79; 
improvements  in,  84 
Gas-mantle:  61,  81;  influence  of, 
99;  characteristics  of,  100  et 
seq.;  187 

Gas-meter,  Clegg’s,  76 
Gasolene:  lamps,  55;  57 
Gassiot,  114 


362 


INDEX 


Gauss,  196 
Geissler,  146 

General  Electric  Company,  132, 
135,  136 

Germany:  development  of  lamps 
in,  56 ;  early  gas-lighting  in,  72 
Glass,  195,  290  et  seq. 

Glowers,  139 
Glow-worms,  24 
Glycerides,  52 
Gold,  293 
Gout,  275 

Gramme  dynamo,  117 
Grass:  18;  carbon  filaments,  129 
Greece:  39;  sacred  lamps  in  an¬ 
cient,  41 ;  42 

Greenhouses,  carbon-filament  lamp3 
in,  250  et  seq. 

Hall  of  Fame,  134 
Happiness,  effect  of  artificial  light 
upon,  14 

Hayden  and  Steinmetz,  253 
Health,  artificial  light  in  relation 
to,  269-283 
Helium,  89 
Hemig,  155 
Hemp,  21 

Henry,  William,  75 
Herodotus,  56 
Hertz,  68 

Hertzian  waves,  271 
Hewitt,  Cooper,  produces  mercury- 
arcs,  124,  125 

Home:  artificial  light  in  relation 
to,  6;  lighting,  325  et  seq. 
Hindu:  light  in,  ceremonials,  40 
Hudson-Fulton  Celebration,  306 
Huygens,  195 
Hydrocarbons,  82 
Hydrogen,  81 

Illiteracy,  artificial  light  and,  9 

Invention,  7,  97 

Iowa,  238 

Iridium,  129 

Iron,  18,  262,  294 

Iron  pvrites,  18 

Italy,  249 

Jablochkov:  electric  candle  of,  117 
Jamaica,  19 


Jandus,  118,  122 

Japan:  19;  use  of  oil  in,  30;  281 
Jerusalem,  43 

Jews:  artificial  light  among,  40 
Journal ,  Paris,  quoted,  210-212 

Kerosene :  57 ;  weight  of,  lumens, 
60;  62,  187,  233 

Ivitson,  platinum-gauze  mantle  ap¬ 
plied  by,  61 

Laboratories:  achievements  of,  137 
Lamps:  16,  25;  Roman,  30;  31; 
invention  of  safety,  33;  ancient 
funereal,  39 ;  sacred,  of  an¬ 
tiquity,  41;  ceremonial,  44; 
scientific  development  of  oil,  51 
et  seq.;  Holliday,  55;  Carcel,  54, 
55;  Franchot’s  moderator,  55; 
gasolene,  55;  development  of,  in 
Germany,  56;  air  pressure,  61; 
supremacy  of  oil,  ends,  62;  Bow- 
ditch’s,  77,  78;  80,  97;  mercury- 
arc,  126;  electric  incandescent 
filament,  127  et  seq.;  gem,  132; 
tungsten,  133  et  seq.;  luminous 
efficiency  (table)  of  incandescent 
filament,  141;  299;  in  home, 
328-333 
Lange,  167 
Lard-oil,  51 
Lavoisier,  195 
Lead,  262,  294 
LeBon,  72 

“Legend  of  Montrose,  The,”  Scott, 
cited  on  primitive  lighting,  27 
Leigh,  Edmund,  quoted,  226 
Lenses,  20,  171  et  seq. 

Libanius,  quoted,  153,  154 
Liberty,  Statue  of,  301,  302,  303 
Libraries,  9 

Light:  relation  of  artificial,  to 
progress,  3  et  seq.;  as  a  civiliz¬ 
ing  agency,  3-14;  primitive  man 
and  artificial,  4;  Milton,  quoted 
on  importance  of,  5;  artificial, 
and  science,  7 ;  artificial,  and 
industrial  development,  8;  Mae¬ 
terlinck’s  tribute  to,  9;  Lincoln’s 
debt  to  artificial,  9 ;  symbolism 
of,  9,  10;  therapy,  10;  in  war, 
11;  adaptations  of,  12;  13; 


INDEX 


363 


mythical  origin  of  artificial,  16; 
earliest  source  of,  16;  production 
of,  in  stone  age,  18;  matches  as 
source  of,  21;  animals  as, 
sources,  24,  25 ;  primitive 

sources  of,  24-37 ;  evolution  of 
artificial,  sources,  24-37 ;  devel¬ 
opment,  28  et  seq .;  early  outdoor 
use  of  artificial,  28;  Homan  uses 
of  artificial,  30;  beginning  of 
scientific,  33,  34;  candles  as 
modern,  source,  36,  37;  symbol¬ 
ism  and  religious  uses  of,  38 
et  seq.;  Bible  cited  on  artificial, 
42-44;  in  relation  to  worship, 
43,  45,  46;  Argand’s  contribu¬ 
tion  to,  53,  54;  coal  as,  source, 
55;  early  uses  of  gas  as,  source, 
63  et  seq.;  as  a  public  utility, 
70;  first  installation  of  indus¬ 
trial  gas,  72;  science  of,  pro¬ 
duction,  80  et  seq.;  causes  of, 
radiation,  80,  81;  83;  lime,  84; 
electric,  89  et  seq.;  principle  of, 
production,  90,  91;  sources,  93; 
various  gas-burners’,  supply,  95; 
relative  efficiency  of,  sources,  95, 
96;  in  the  home,  97;  influence 
of,  upon  science,  invention,  and 
commerce,  97  et  seq.;  yield  of 
acetylene,  106,  107;  electric, 

109;  influence  of  gas  upon  de¬ 
velopment  of  artificial,  110;  de¬ 
velopment  of  artificial,  111  et 
seq.;  efforts  to  improve  color  of 
mercury-arc,  125;  electric-incan¬ 
descent-filament,  127  et  seq.;  ef¬ 
fect  of  tungsten,  upon,  133  et 
seq.;  of  the  future,  143-152;  in 
warfare,  178-193;  signaling, 
194-207;  cost  of,  208-224;  and 
safety,  225  et  seq.;  improper  use 
of,  229,  230;  comparison  of  day¬ 
light  and  artificial,  240;  reduc¬ 
ing  action  of,  258 ;  bactericidal 
action  of,  272  et  seq.;  modify¬ 
ing,  284  et  seq.;  spectacular  uses 
of,  298-309;  expressiveness  of, 
310-324;  utility  of  modern, 
325-340;  evolution  of  the  art  of 
applying,  34 1-356;  mobile,  347, 
348,  349,  350;  psychological  ef¬ 


fect  of,  351  et  seq.;  as  an  accom¬ 
paniment  to  music,  352-354 
Liglit-buoys,  10,  169 
Lighthouses:  10,  163-177;  optical 
apparatus  of,  172  et  seq. 
Light-ships,  10,  169 
Lighting-systems:  comparison  of, 
12-14 

Lime,  84,  107,  108,  294 
Lincoln,  Abraham,  9 
Linen,  18 
Link-buoys,  28 
Lithopone,  265,  266 
Liverpool,  167 

Living:  comparison  of,  standards, 
238  et  seq. 

London,  152,  154,  155,  156,  157, 
202 

London  Gas  Light  and  Coke  Com¬ 
pany,  74 
Lucigen,  61 

Lumen-hour:  defined,  215 
Lumens:  60,  94,  215 
Lutheran  Church,  49 
Lyceum  Theatre,  London,  73 


Maeterlinck,  Maurice,  9 
Magazines,  8 
Magdsick,  H.  H.,  303 
Magnesia:  84;  Nernst’s  applica¬ 
tion  of,  138 
Magnesium,  179,  180 
Magnetite  arc,  187 
Man:  distinction  between,  and  ani¬ 
mal,  3;  artificial  light  and 
early,  4;  light-sources  of  primi¬ 
tive,  25 

Manganese,  262,  268,  294 
Mangin,  188 
Mann,  129 
Mantles,  95 
Manufacturing,  8 
Marconi,  68 
Marks,  118 

Matches:  as  light-sources,  21;  22, 
82 

Maxwell,  68 

Mazda  lamps,  289,  339 

Mecca,  40 

Mediterranean  Sea,  163 
Mercury-arc:  Way’s,  124;  125, 


364 


INDEX 


126;  quartz,  125,  126;  attempts 
to  improve  color  of,  light,  125 
Middle  Ages,  46,  47,  474 
Milton,  quoted,  5 
Mirror,  19 
Mohammedans,  40 
Moore,  Dr.  McFarlan,  146,  147 
Morality,  effect  of  light  upon,  9 
Morse  code:  application  of,  to 
light-signaling,  198,  199 
Moses,  195 

Moving-pictures,  9,  260,  261 
Munich,  72 

Murdock,  William:  installment  of 
gas-pipes  by,  63;  68,  69,  70; 
quoted  on  industrial  use  of  arti¬ 
ficial,  71;  72,  73,  74,  76,  78,  217, 
309 

Museums:  13;  utilization  of  arti¬ 
ficial  light  by,  322,  323 
Music:  light  as  an  accompaniment 
to,  352-354 
Mythology,  16 

Nantes,  85 
Napoleon,  111 
Napthalene,  106 

National  Heat  and  Light  Co.,  72, 
74 

Natural  gas,  99 
Navesink  Light,  206 
Nernst,  138,  139 
Newspapers,  8 

Newton,  Sir  Isaac:  7;  quoted  on 
discoverv  of  visible  spectrum, 
87;  88 

New  York,  98,  165,  166,  206,  302, 
304 

Niagara  Falls,  108,  306 

Nickel,  262 

Nielson,  77 

Niepce,  258 

Niter,  21 

Nitrogen,  137 

Norfolk,  169 

Obesity,  275 
Offices,  13 

Oil:  as  a  light-source,  29  et  seq.; 
development  of,  lamps,  51  et 
seq.;  155;  in  lighthouse,  165  et 
seq.;  222,  224,  299 


O’Leary,  Mrs.,  and  her  lamp,  62 
Olive-oil,  51,  52,  167 
Orkney  Islands,  29,  177 
Osmium,  133 

Oxygen:  relative  consumption  of, 
by  oil-lamps,  58,  59;  262 
Ozone,  262 

Painting,  342,  343,  347,  348,  349 
Pall  Mall,  74 

Panama-Pacific  Exposition :  304 ; 
artificial  lighting  of,  306,  307, 
308,  309 

Paper:  18;  carbon  filaments,  129, 
130 

Paraffin,  35,  57 
Parker  and  Clark,  139 
Paris:  experimental  gas-lighting 
in,  83,  84;  Volta  in,  111;  154, 
185,  210,  212,  213 
Peckham,  John,  195 
Pennsylvania:  discovery  of  oil  in, 
56 

Periodic  Law,  145 
Petroleum:  35,  51,  55;  discovery 
of,  56 ;  constitution  of  crude,  57 ; 
58,  214 
Pharos,  163 

Philadelphia,  98,  99,  157 
Phillips  and  Lee,  70,  72 
“Philosophical  Transactions  of  the 
Royal  Society  of  London,”  33; 
quoted  on  industrial  lighting, 
63;  Shirley’s  report  on  natural 
gas  in,  66,  67 ;  quoted,  87 
Phoenicians,  34,  39 
Phosphorus,  21 
Photo-micography,  12 
Photography:  126;  early  experi¬ 
ments  in,  258;  development  of, 
259;  291,  292 
Picric  acid,  106 
Pigments,  265 

Pintsch:  production  of,  gas,  109, 
110,  170 
Pitch,  106 

Plant-growth:  artificial  light  and, 
11,  249  et  seq. 

Platinum,  85,  128,  129,  262 
Plumbago,  113,  130 
Plymouth,  166 
Poetry,  346 


INDEX 


365 


Police,  162 

Potash,  chlorate  of,  22 
Priestley,  Professor,  quoted,  252 
Printing,  8 

Progress:  influence  of  fire  upon, 
15  et  seq. 

Prometheus,  16,  41 
Propylene,  106 
Ptolemy  II,  163 

Quartz:  18,  19;  mercury-arcs,  125; 
uses  of,  126;  in  skin  diseases, 
278,  279 

Radiators,  energy,  88  et  seq. 
Radium,  150 

Railway  Signal  Association,  205 
Railways:  light-signaling  applied 
to,  205 

Ramie  fiber,  101 
Rane,  250,  251 

Rare-earth  oxides:  85;  properties 
of,  88,  99 
Recreation,  9 
Redruth,  63 

Reformation :  ceremonial  uses  of 
light  during  the,  48,  49 
Rheumatism,  275 
Robins,  Benjamin,  201 
Rome,  30,  32,  34,  39,  41,  42,  44 
Rontgen,  270,  280.  See  also  X- 
ray. 

Royal  Society  of  London:  33,  63, 
66,  67,  70,  73;  and  first  gas  ex¬ 
plosion,  75,  111,  112 
Rumford,  167 
Rushlights,  28,  33 
Russia,  281 
Ryan,  W.  D’A.,  306 

Safety:  artificial  light  in  relation 
to,  14,  225  et  seq. 

Salts:  chemical,  88,  89;  metallic, 
120;  silver,  257,  258 
Sandy  Hook  Light,  165,  166 
San  Francisco,  304,  306-309 
Savages,  3,  15,  17 
Sawyer,  129 

Scheele,  K.  W.,  133;  quoted,  257, 
258 

Schools,  9 


Science:  light  and,  6,  7;  97;  sys¬ 
tematized,  268 

Scotland:  26,  31,  32,  48;  oil  in¬ 
dustry  in,  56 

Scott,  Sir  Walter,  cited,  27,  98 
Sculpture:  artificial  light  in  rela¬ 
tion  to,  184 
Search-lights,  11,  169 
Section  of  Plant  Protection,  225, 
226 

Selenium,  267,  293 
Semaphore,  199 

Shells:  illuminating,  179  et  seq. 
Shirley,  Thomas:  quoted  on  natu¬ 
ral  gas,  66,  67 
Siemans,  78 
Signaling,  194-207 
Silicon:  filament,  140 
Silk:  artificial,  101;  carbon-fila¬ 
ments,  129 

Simpson,  R.  E.,  227,  231 
Silver,  258,  293 

Skin  diseases:  treatment  of,  278, 
279,  280 
Skylights,  13 
Sleep,  8 

Smallpox,  274,  275 
Smeaton,  166 
Soho,  69,  72 
South  Africa,  129 
Sparks:  33,  125 

Spectrum:  visible,  86;  Newton 
quoted  on,  87 ;  of  elements,  89 ; 
of  gases,  90;  120,  121;  mercury, 
124-126 

Sperm,  31,  51,  52,  167 
Spermaceti,  35,  51 
Splinter-holders,  27,  28 
Stage:  and  artificial  light,  319 
et  seq.;  343 
Staite,  117,  118 
Stearine,  35,  52 
Steam,  129 
Steel,  18,  33 

Steinmetz,  Hayden  and,  253 
Sterilization :  quartz-mercury-arc 

and,  280,  281,  282 
Stevenson,  Robert  Louis,  quoted, 
177 

Stores,  13 
St.  Paul,  43 

St.  Paul’s  Cathedral,  300 


366 


INDEX 


Street-lighting :  development  of, 
152-162 
Sugar,  22 

Sulphide  of  iron,  18 

Sulphur,  18,  21,  179,  180,  294 

Sulphuric  acid,  21,  22 

Sun,  8,  16,  19,  20 

Swan,  129 

Syracuse,  19 

Syria,  153 

Tallow,  34,  35,  51,  52 
Tantalum:  132;  filament  lamps, 
133 

Tar,  68,  106 
Telegraphy,  195 
Telephony,  194 
Textiles,  256 
Thames,  169 
Theaters,  9,  319  et  seq. 

Thoria,  85 
Tin,  262 

Tinder-boxes,  18,  19,  22 
Travelers  Insurance  Company,  227 
Trees,  26 
Troy,  42 
Tuberculosis,  273 

Tungsten  lamp,  161  et  seq.,  187, 
261,  290,  303 
Typhus,  273 

Ultra-violet  rays:  126,  150;  in 
photographic  electricity,  267, 
268;  270,  272,  294 
United  States :  petroleum  in,  57 ; 
gas-consumption  in,  99;  164, 

165,  166 

United  States  Geological  Survey, 
cited  on  sale  of  gas,  222 
United  States  Military  Intelli¬ 
gence,  225,  226 

Vacuum  tubes,  81,  286 
Venetians,  195 
Ventilation,  13 
Verne,  Jules,  143 


Vestal  Virgins,  42 
Volcanoes,  166 
Volta,  111,  112,  127 
Voltaic  pile:  construction  of,  111, 
127 

Von  Bolton.  See  Bolton. 

War:  and  artificial  light,  11,  178- 
193 

Washington,  305 

Water:  sterilization  of,  by  arti¬ 
ficial  light,  280  et  seq. 

Watson,  Dr.  Richard,  67,  68 
Watt,  94 

Waves :  electro-magnetic,  68,  86, 
125  et  seq. 

Wax,  34,  46,  51 

Way :  mercury-arc  produced  by, 
124 

Wells,  61 

Wells,  H.  G.,  cited,  148 
Welsbach,  Auer  von:  61;  invention 
of  mantle  by,  99,  100,  133 
Wenham,  78 
West  Indies,  25 
Whale-oil,  31 

Wicks,  35,  36,  53,  54,  58,  59 
Winsor,  72,  73.  See  also  Winzler. 
Winzler.  See  Winsor. 

Wolfram.  See  Tungsten. 

Wood,  26,  27,  28 
Woolworth  Building,  302,  303 
Wounds:  treatment  of,  by  artifi¬ 
cial  light,  10 

X-rav :  production  of,  tubes  dur¬ 
ing  War,  131;  137,  150,  270,  280 

Young,  James:  discovers  petro¬ 
leum,  56 
Yttria,  85 

Zeitung,  Cologne:  157;  extract 
from,  on  street-lighting,  158 
Zinc,  125,  130,  267 
Zirconia,  84,  85 


GETTY  CENTER  LIBRARY  CONS 

TP  715  L94  1920  61(5 

c  i  Luckiesh,  Matthew,  b 

Artificial  light  :  its  influence  upon  ci 


3  3125  00312  5271 


